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Old 12-19-2003, 12:00 PM   #1 (permalink)
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OBD I ECU Anatomy
Thanks to Hondata
www.hondata.com

Introduction

The Honda ECU, like your Honda engine, is a very well designed piece of equipment made to work in many cars under many varying conditions of temperature and altitude. This tech article looks at the functions of the ECU and how it differs from some of the piggyback and standalone systems available.
Backup Microprocessor

The backup microprocessor monitors the function of the main microprocessor, ROM and sensors. In the event of a serious failure it takes over the running of the computer in what is called limp home mode. In this mode the ECU needs only two sensors to run. TDC (top dead center from the distributor) and TPS (throttle position). In fact you can remove entirely the ROM and primary microprocessor and your Honda will still run. Limp home mode is rev limited to 3500 RPM with a fixed ignition and rather rich fuel setting with the engine check light permanently on.

This is military specification redundancy designed to keep you going even in the event of multiple sensor failures. No other vehicle maker we are aware of uses a backup processor and this level of redundancy.
Analog Input

This is where the 12V signals are conditioned and converted into 5V for processing - such as the distributor signals TPS and MAP.
Analog Output: Injector driver transistors

These are excellent quality transistors, which make a substantial contribution to how the well the Honda ECU drives injectors. These transistors do not even get warm (except when low impedance resistors are incorrectly wired in without the Honda resistor box!). All Honda ECUs drive high impedance injectors or low impedance injectors with an external resistor box.

Hondas switch the injectors on and off rapidly (red line). With poorer quality transistors the injectors do not open or close as quickly, resulting in less fuel delivered in the same amount of time. The difference is most noticeable at small injector durations - part throttle.

Increase your fuel pressure and the extra fuel line pressure can slow the injector opening. Another reason to keep low fuel pressures.

Larger injectors with a heavier pintle also take longer to open and close due to inertia and show a similar effect.

We have found Honda ECUs work particularly well with larger injectors. For example one Hondata customer using 830 cc injectors in a B20 turbo has drivability indistinguishable from stock and achieves 30mpg.
Barometric Air Pressure sensor

This sensor tells the ECU at what altitude you are running. The ECU uses this information to make small fuelling adjustments at altitude. This is one of the reasons for Honda excellent idle and part throttle characteristics in all conditions.
Interpolation



Interpolation is the process the computer goes through to calculate the fuel and ignition values between the marked points on the fuel and ignition map. For example, what fuel value should be used at 800 RPM at 400 mb of air pressure? The mathematics are the same for the Honda or any standalone, but there can be differences on how the ECU turns that number into an injector opening time.

The Honda (red line) times the injector opening and closing time to an accuracy of about a millionth of a second, which on a 1ms pulse width is an accuracy of 0.1 % e.g., 96.1, 96.2 ...165.9, 166. Many standalone systems (black line in the diagram above) step the injectors as little as 8 or 16 times - 96, 100, 104 ... 162, 166. This step is probably the result of digital to analog conversion.

There are two schools of thought on this.

* The first is that the differences between the two are too small to be significant.
* The second is that Honda must do this for a reason.

Fuel injection specialists support the second school of thought saying that Honda's precise injector control contributes to driveability compared to some standalone systems with a stepped output for injector duration.
Fuel and ignition maps

VTEC Honda ECUS have two complete and independant fuel and ignition maps for each camshaft. We are not aware of any standalone that has this capability.

Having 2 maps makes the tuning process very straight forward.

* Set the VTEC point to 7000 RPM and tune the low speed cam fuelling and ignition
* Set the VTEC point to 3000 RPM and tune the high speed cam camshaft.
* Plot the torque curves and set the VTEC point to the crossover RPM

This method ensures a very smooth VTEC transition (some JR customers have complained their VTEC was not working when it in fact was)

Be aware that stock Honda ECUs have 10 VTEC points, not one, and at light throttle the VTEC point can be 1000-1500 RPM higher than at full throttle. If you are running with a standalone with one ignition and fuel map and have a variable VTEC point (or a piggyback with a fixed VTEC point), then you cannot have the correct fuelling and timing for both cams all the time.

Variable load and RPM scaling.

Honda scale their RPM points closer together where needed for fine tuning (see the red lines and arrows below). For example at idle and VTEC crossover the RPM points are 200-250 RPM apart. At high RPM the tuning points can be as far apart as 500 RPM. The same goes for load, although it is not as easy to see on these graphs.

What the graphs from this 95 GSR mean:

* The low speed and high speed fuel and ignition curves are vastly different.

* The shape of the fuel curves are very closely related to torque.

* After peak torque, less fuel is needed as can be seen below in the low speed cam fuel curve after 6000 RPM.





VTEC controllers

The ECU switches maps when the high speed VTEC cam is engaged. When an external VTEC controller is added, the cam is switched with the ECU running on the incorrect map for that cam. Depending on the RPM you can be as much as 10% fuel and 6 degrees ignition timing out. A typical VTEC controller will adjust 8 RPM positions by 2 load positions for a total of 16 tuning points. Compare that to 20 RPM positions by 10 load positions for each cam for a total of 400 tuning points. (* this is for a stock ECU. Hondata adds 240 tuning points for boost)

So in summary, external VTEC controllers upset the stock fuelling and ignition by switching the cam, have no ignition correction and very coarse fueling correction compared to the stock ECU.

Short and long term fuel trim.

OBD I and OBD II both have a function called fuel trim. If, at part throttle the ECU sees the air fuel ratio is too rich or lean the ECU makes immediate (short term) corrections. Over time those corrections are learned and transferred to a long term trim value that is applied all the time. Unplugging the ECU is one only way of erasing the long term value. So depending on how you alter the fuel with an external piggyback type controller, the ECU can learn and override it.


Article on hondata:
http://www.sportcompactcarweb.com/pr...c_projciviceg/
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Old 12-19-2003, 12:14 PM   #2 (permalink)
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ECU Identification
http://hondata.com/techecuid.html

To identify your ECU you will need to know its generation, part number and possibly its ROM number.

The ECU can be located in several places: under a metal plate in the passenger's footwell (models up to 91), in the passenger's footwell behind a plastic panel (models 92-99) or by the driver's footwell under a plastic panel (some models 2000+)

The computer is connected via three connectors that pull out when a plastic clip is pressed. Remove the computer, and with a philips screwdriver remove the metal lid from the top of the computer. There may be small daughter circuit board covering some of the main circuitry. Unscrew this and lift it out of the way.
ECU Generations

Honda ECUs run in generations, which use different connectors. Below is a stack of ECUs running from the newest generation at the top to the oldest generation at the bottom.

*****Image is below*****




ECU Part Numbers

All Honda ECUs have a part number which is located on the side of the ECU and inside the ECU on the connector. e.g. 37820-P72-A01

The part number consists of three components:

* Honda's part number for ECU, which is always 37820
* Three characters (which are loosely related to the model of car/engine). e.g P72
* Three characters (which are the revision of the ECU) e.g. A01

The middle three characters are the most useful to identify what the ECU is. Different generation ECUs may use the same characters. e.g. a P72 OBD I ECU is different from a P72 OBD II ECU. Here is a list of common ECUs:

* PG6 : 88-89 Integra (all makes)
* PM5 : 88-91 Civic/CRX DX
* PM6 : 88-91 Civic/CRX SOHC Si
* PM7 : 89-91 DOHC ZC (JDM 'EF' ECU)
* PM8 : 88-91 CRX HF
* PR2 : 89-91 ZC (Euro)
* PR3 : 89-91 JDM B16A EF8/9
* PR3 -J00 or J51 : 92 JDM Integra B16A EF8/9
* PW0 : 89-91 JDM B16A EF8/9 DA6-XSi
* PR4 : 90-91 Integra LS/GS
* PS9 : 88-91 4 door Civic EX Auto
* P05 : 92-95 OBD-1 Civic CX
* P06 : 92-95 OBD-1 Civic DX
* P07 : 92-95 OBD-1 Civic VX
* P08 : 92-95 OBD-1 Civic D15 JDM
* P0A : 94-95 OBD-1 Accord EX
* P13 : 93-95 OBD-1 Prelude Vtec
* P14 : 93-95 OBD-1 Prelude Si (non Vtec)
* P27 : 92-95 OBD-1 EG JDM Civic 1600 sohc
* P28 : 92-95 OBD-1 Civic Si/Ex
* P30 : 92-95 OBD-1 DelSol DOHC Vtec Si/EG SiR
* P54-G31 : 1997 Honda Accord 1.8 LS
* P61 : 92-93 OBD-1 Integra GSR
* P72 : 94-95 OBD-1 Integra GSR
* P72 : 96-00 OBD-2 Integra GSR
* P73 : 96-00 OBD-2 Integra Type-R (JDM & USDM)
* P74/75: 92-95 OBD-1 Integra LS/GS
* P75 : 96-00 OBD-2 Integra LS/GS
* P2N : 96+ OBD-2 Civic HX Coupe
* P2P : 96+ OBD-2 Civic EX Coupe
* P2E : 96+ OBD-2 Civic DX Coupe
* P2M : 96+ OBD-2 NZ Civic SOHC VTEC
* P2T : 99+ OBD-? Civic Si Coupe
* P5P : 97-00 OBD-2 Prelude Type-S (JDM ECU)
* PBA : 97+ US Acura 1.6EL
* PCT : 98+ JDM ITR / CTR
* PCX : 99+ OBD-? S2000

ECU ROM Numbers

As further identification Honda ECUs have a software revision number inside the ECU. This is usually a two or three digit number stamped on the 28 pin ROM, or main processor. Accord and Prelude ECUs can use a letter and number code.
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Old 12-19-2003, 12:27 PM   #3 (permalink)
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From 2 sources
From Hondata:
OBD1 ECU
http://www.hondata.com/techecuanatomy.html
Thanks to Hondata
www.hondata.com

OBD1 ECU Codes
Code Meaning
1 O2A - Oxygen sensor #1
2 O2B - Oxygen sensor #2
3 MAP - manifold absolute pressure sensor
4 CKP - crank position sensor
5 MAP - manifold absolute pressure sensor
6 ECT - water temperature sensor
7 TPS - throttle position sensor
8 TDC - top dead centre sensor
9 CYP - cylinder sensor
10 IAT - intake air temperature sensor
12 EGR - exhaust gas recirculation lift valve
13 BARO - atmospheric pressure sensor
14 IAC (EACV) - idle air control valve
15 Ignition output signal
16 Fuel injectors
17 VSS - speed sensor
19 Automatic transmission lockup control valve
20 Electrical load detector
21 VTEC spool solenoid valve
22 VTEC pressure valve
23 Knock sensor
30 Automatic transmission A signal
31 Automatic transmission B signal
41 Primary oxygen sensor heater
43 Fuel supply system
45 Fuel system too rich or lean
48 LAF - lean air fuel sensor
54 CKF - crank fluctuation sensor
58 TDC sensor #2
61 Primary oxygen sensor
63 Secondary oxygen sensor
65 Secondary oxygen sensor heater



Honda ECU Trouble Codes

1 Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 97-98 85-91 93-97 95-98 85-98
Oxygen Sensor "A" (Primary)
defective circuit or unplugged / defective sensor

2 Accord Civic CRV CRX Del Sol Odyssey Prelude
85-89 86-87 n/a 85-87 85-91 n/a n/a
Oxygen Sensor "B"
defective circuit or unplugged / defective sensor

3 Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 97-98 85-91 93-97 95-98 85-98
MAP Sensor (Manifold Absolute Pressure)
defective circuit or unplugged / defective sensor

4 Accord Civic CRV CRX Del Sol Odyssey Prelude
90-98 88-98 97-98 88-91 93-97 95-98 85-98
CKP Sensor (Crankshaft Position Sensor)
defective circuit or unplugged / defective sensor

5 Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 * 86-98 97-98 85-91 93-97 96-98 85-98
MAP Sensor (Manifold Absolute Pressure)
mechanical problem / disconnected piping
* exc 94-95

6 Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 97-98 85-91 93-97 95-98 85-98
ECT Sensor (Engine Coolant Temperature)
defective circuit or unplugged / defective sensor

7 Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 97-98 85-91 93-97 95-98 85-98
TP Sensor (Throttle Position)
defective circuit or unplugged / defective sensor

8 Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 97-98 85-91 93-97 95-98 85-98
TDC Sensor (Top Dead Center)
defective circuit or unplugged / defective sensor

9* Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98** 86-98 97-98 85-91 93-97 95-98 85-98
CYP Sensor (Cylinder)
defective circuit or unplugged / defective sensor
* not a valid code for any throttle body injection Hondas
** not a valid code for V-6 engines

10 Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 97-98 85-91 93-97 95-98 85-98
IAT Sensor (Intake Air Temperature)
defective circuit or unplugged / defective sensor

12 Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 * n/a 85-91 * n/a 95-98 85-98
EGR Lift Sensor (Exhaust Gas Recirculation)
defective circuit or unplugged / defective sensor
* not a valid code if car is not equipped with an EGR valve (some Civic models are not)

13 Accord Civic CRV CRX Del Sol Odyssey Prelude
85-98 86-98 97-98 85-91 93-97 95-98 85-98
BARO Sensor (Atmospheric Pressure)
defective circuit or unplugged / defective sensor

14 Accord Civic CRV CRX Del Sol Odyssey Prelude
88-98 88-98 97-98 88-91 93-97 95-98 88-98
IAC Valve (Idle Air Control)
defective circuit or unplugged / defective sensor

15 Accord Civic CRV CRX Del Sol Odyssey Prelude
90-95 88-95 n/a 88-91 93-95 95 88-95
Ignition Output Signal
missing or defective ignition output signal

16 Accord Civic CRV CRX Del Sol Odyssey Prelude
90-95 88-95 n/a 88-91 93-95 95 88-95
Fuel Injector System
defective circuit or unplugged / defective fuel injector

17 Accord Civic CRV CRX Del Sol Odyssey Prelude
88-98 88-98 97-98 88-91 93-97 95-97 88-98
VSS (Vehicle Speed Sensor)
defective circuit or unplugged / defective sensor

19 Accord Civic CRV CRX Del Sol Odyssey Prelude
n/a 88-95 n/a 88-91 93-97 n/a n/a
Automatic Transmission Lock Up Control Solenoid Valve
defective circuit or unplugged / defective solenoid valve

20 Accord Civic CRV CRX Del Sol Odyssey Prelude
90-98 88-98 97-98 88-91 93-97 95-98 92-98
Electrical Load Detector
defective circuit or unplugged / defective sensor

21* Accord Civic CRV CRX Del Sol Odyssey Prelude
94-98 ** 92-95 n/a n/a 93-95 n/a 93-95
VTEC Solenoid Valve
defective circuit or unplugged / defective solenoid valve
* not a valid code if car does not have a VTEC engine
** not with V-6 engine

22* Accord Civic CRV CRX Del Sol Odyssey Prelude
94-98 92-98 n/a n/a 93-97 98 93-98`
VTEC Oil Pressure Switch
defective circuit or unplugged / defective oil pressure switch
* not a valid code if car does not have a VTEC engine

23 Accord Civic CRV CRX Del Sol Odyssey Prelude
98 * 96-98 n/a n/a 94-97 n/a 92-98
KS (Knock Sensor)
defective circuit or unplugged / defective sensor
* not a valid code if V-6 engine

30 Accord Civic CRV CRX Del Sol Odyssey Prelude
90-98 * n/a n/a n/a n/a 95 92-98 *
Automatic Transmission Signal: "A" / SEAF / SEFA / TMA or TMB
defective circuit or unplugged / defective sensor
* not a valid code for 1996

31 Accord Civic CRV CRX Del Sol Odyssey Prelude
90-95 n/a n/a n/a n/a 95 92-95
Automatic Transmission Signal "B"
defective circuit or unplugged / defective sensor

41 Accord Civic CRV CRX Del Sol Odyssey Prelude
90-98 92-98 97-98 n/a 93-97 95-98 90-98
Primary Oxygen Sensor - Heater
circuit malfunction

43 Accord Civic CRV CRX Del Sol Odyssey Prelude
90-95 92-95 n/a n/a 93-95 95 90-95
Fuel Supply System
defective or malfunctioning fuel supply system

45 Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
System Too Lean or Too Rich
malfunction in the fuel monitoring systems

48 Accord Civic CRV CRX Del Sol Odyssey Prelude
98 92-98 n/a n/a n/a n/a n/a
LAF Sensor (Lean Air Fuel)
defective circuit or unplugged / defective sensor

54 Accord Civic CRV CRX Del Sol Odyssey Prelude
96 96-98 97-98 n/a 96-97 n/a n/a
CKF Sensor (Crankshaft Speed Fluctuation)
defective circuit or unplugged / defective sensor

58 Accord Civic CRV CRX Del Sol Odyssey Prelude
98 * n/a n/a n/a n/a n/a n/a
TDC Sensor 2 (Top Dead Center)
defective circuit or unplugged / defective sensor
* with V-6 engine only

61 Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Oxygen Sensor, Heated - Sensor 1 (Primary)
high voltage, low voltage, or slow response

63 Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Oxygen Sensor, Heated - Sensor 2 (Secondary)
high voltage, low voltage, or slow response

65 Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Oxygen Sensor Heater (Secondary)
malfunctioning or defective oxygen sensor heater

67 Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Catalyst system Efficiency Below Threshold
malfunctioning or defective catalyst system

70 Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a n/a 96-98 96-98
Automatic Transmission
malfunction with the automatic transmission controls

71 Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Cylinder 1 Misfire or a Random Misfire
a condition is present that is creating a cylinder misfire

72 Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Cylinder 2 Misfire or a Random Misfire
a condition is present that is creating a cylinder misfire

73 Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Cylinder 3 Misfire or a Random Misfire
a condition is present that is creating a cylinder misfire

74 Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
Cylinder 4 Misfire or a Random Misfire
a condition is present that is creating a cylinder misfire

75 Accord Civic CRV CRX Del Sol Odyssey Prelude
98 * n/a n/a n/a n/a n/a n/a
Cylinder 5 Misfire or a Random Misfire
a condition is present that is creating a cylinder misfire
* valid code for V-6 engine only

76 Accord Civic CRV CRX Del Sol Odyssey Prelude
98 * n/a n/a n/a n/a n/a n/a
Cylinder 6 Misfire or a Random Misfire
a condition is present that is creating a cylinder misfire
* valid code for V-6 engine only

80 Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 n/a n/a n/a 96-98 96-98
Exhaust Gas Recirculation
insufficient flow detected

86 Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-98 96-98
ECT Sensor (Engine Coolant Temperature)
circuit range / performance problem

90 Accord Civic CRV CRX Del Sol Odyssey Prelude
97-98 96-98 n/a n/a n/a 98 97-98
Evaporative Emission Control System
leak detected in the fuel tank area

91 Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 n/a n/a n/a 98 97-98
Fuel Tank Pressure Sensor
low input

92 Accord Civic CRV CRX Del Sol Odyssey Prelude
96-98 96-98 97-98 n/a 96-97 96-97 96-98
Evaporative Emission Control System
insufficient purge flow

From Helms


OBD0 & OBD1 ECU error codes:
OBD0 Check Engine Light (CEL) Codes
When the Check Engine warning light has been reported on, turn the ignition on, pull down the passenger's side carpet from under the dashboard and observe the LED on the top of the ECU. The LED indicates a system failure code by blinking frequency. The ECU LED can indicate any number of simultaneous component problems by blinking seperate codes, one after another. Problem codes 1 through 9 are indicated by individual short blinks. Problem codes 10 through 44 are indicated by a series of long and short blinks. One long blink equals 10 short blinks. Add the long and short blinks together to determine the problem code.

you have to jump a service connector located on the passenger side right under the dashboard near the door. The connector has two pin inputs. Connecting them with something like a paper clip will force the check engine light on the dashboard to display the codes. when u pull the kick panel on the right side floor board where your ecu you there will be an extra plug hanging i beleive its green or blue, put the paper clip in it, turn the ignition to the on position and count the number of blinks on the check engine light.

codes 1-9 are indicated by a series of short flashes; two digit codes use a number of long flashes for the first digit followed by the number of short flashes for the second digit. So a code 43 will be represented by 4 long and 3 short flashes.

The position of codes in a sequence can be helpful in doing diagnostics. A display showing 1-1-1-pause-9-9-9 indicates two problems occurring at different times. A sequence showing 1-9-1-9-1-9 indicates two problems occurring at the same time.


Note: OBD0 is for ECUs in the years 1988 - 1991.

Self-Diagnosis
Indicator Blinks System Indicated
0 ECU
1, 2 Oxygen Content
3 Manifold Absolute Pressure
4 Crank Angle
5 Manifold Absolute Pressure
6 Coolant
7 Throttle Angle
8 TDC Position
9 No. 1 Cylinder Position
10 Intake Air Temperature
13 Atmospheric Pressure
14 Electronic Air Control
15 Ignition Output Signal
17 Vehicle Speed Sensor
21 Spool Solenoid Valve
22 Oil Pressure Switch
43, 44 Fuel Supply System (KX, KS, KG)


If codes other than those listed above are indicated, count the number of blinks again. If the indicator is in fact blinking unusual codes, subsitute a known-good ECU and recheck. If the indication goes away, replace the original ECU. The Check Engine warning light and ECU LED may come on, indicating a system problem, when, in fact, there is a poor or intermittent electrical connection. First, check the electrical connections, clean or repair connections if necessary. If the Check Engine warning light is on and LED stays on, replace the ECU.
***this was taken from the Helms manual for 88-91 Civics.
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Old 12-19-2003, 12:37 PM   #4 (permalink)
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ECU Pintouts for OBD2b, OBD2a, and OBD1

http://www.autoserve.8m.com/


OBD2a OBD2b Function OBD1 Color Notes
A01 B05 Injector 4 A02 Yellow
A02 B04 Injector 3 A05 Light Blue
A03 B03 Injector 2 A03 Red
A04 B11 Injector 1 A01 Brown
A05 A08 SO2H No connection on OBD1
A06 C01 PO2H A06 Orange/black
A08 B12 VTS A04 Orange/White
A09 B20 LG1 A26 Black/Red
A10 B02 PG1 A23 Black
A11 B01 IGP1 A25 Yellow/Black
A12 B23 IACV A09 Green/White
A15 A06 PCS A20 Red
A16 A16 FLR A07 Green/Yellow
A17 A17 ACC A15 Black/Red
A18 A18 MIL A13 Green/Orange
A19 A02 ALTC A16 White/Yellow No connection on D16Y8 P2Nb
A20 B13 ICM A21 Red/Green
A22 B22 LG2 B02 Brown
A23 B10 PG2 A24 Black
A24 B09 ICP2 B01 Yellow Black
A27 A20 FANC A12 Yellow/Green
C01 C31 CKFP No connection on OBD1
C02 C08 CKPP B15 Blue/Green
C03 C20 TDCP B13 Orange/Blue
C04 C29 CYPP B11 Orange
C05 A27 ACS B05 Blue/Red
C06 A24 STS B09 Blue/White
C07 A10 SCS D04 Brown
C10 B21 VBU D01 White/Blue
C11 C22 CKFM No connection on OBD1
C12 C09 CKPM B16 Blue/Yellow
C13 C21 TDCM B14 White/Blue
C14 C30 CYPM B12 White
C15 C10 VTM D06 Orange/Green Connected to VTS on OBD2a
C16 A26 PSW B08 Brown/Red
C17 C05 ALTF D09 Pink No connection on D16Y8 P2Nb
C18 C23 VSS B10 Yellow/Blue
D01 C27 TPS D11 Pink/Black
D02 C26 ECT D13 Red/White
D03 C17 MAP D17 Pink/White
D04 C19 VCC1 D19 Yellow/Green
D05 A32 BKSM D02 Greem/White
D06 C03 KS D03 Red/Green No connection on P08, P28
D07 C16 PO2S D14 White
D08 C25 IAT D15
D10 C28 VCC2 D20 Yellow/White
D11 C18 SG2 D22 Green/White
D12 C07 SG1 D21 Green/Blue
D14 A23 SO2S No connection on OBD1
D16 A30 EL D10 Green/Red No connection on D16Y8 P2Nb



Dyno Chart for some chips:
http://www.autoserve.8m.com/ChipDyno.html
How to install a Chip on 88-91 OBD-0 Honda ECU
http://www.autoserve.8m.com/StepBySt...ion_OBD_0.html
How to install a Chip on 92-95 OBD-I Honda ECU
http://www.autoserve.8m.com/StepBySt...ion_OBD_I.html
How to install a Chip on 96-up OBD-II Honda ECU
http://www.autoserve.8m.com/StepBySt...on_OBD_II.html
ECU INFO CENTER
http://www.autoserve.8m.com/Ecu_Info.html
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Old 12-21-2003, 01:10 AM   #5 (permalink)
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Wiring Conversion 99Si to OBD1
http://www.hasport.com/Tech/Wring/Co...i%20-OBD1.htm#

OBD 2.5 / OBD 1 / Terminal descrption

B11 A1 #1 injector
B3 A3 #2 injector
B4 A5 #3 injector
B5 A2 #4 injector
B1 A25 IGN power 1 for ECU
B9 B1 IGN power 2 for ECU
B2 A23 Power ground 1 for ECU
B10 A24 Power Ground 2 for ECU
B20 A26 Logic Ground 1 for ECU
B22 B2 Logic ground 2 for ECU
A6 A20 EVAP Purge control solenoid valve
A29 - Fuel tank pressure sensor
B12 A4 VTEC solenoid
- - Fuel pressure solenoid vlave
A16 A7 Fuel pump relay
- - Fuel pump relay
A18 A13 Malfunction indicator lamp
B13 A21
- - Igniter
B23 A9 IACV (EACV)
C16 D14 Primary O2 signal
C1 A6 Primary HO2 heater control
A23 - Secondary O2 signal
A8 - Secondary HO2 heater control
- A17 IAB (GSR)
A20 A12 Radiator fan control
- - Tandem valve control solenoid
C22 - CKF P
C31 - CKF G
C8 B15 CKP P
C9 B16 CKP G
C20 B13 TDC P
C21 B14 TDC G
C29 B11 CYP P
C30 B12 CYP G
A17 A15 A/C clutch relay
A27 B5 A/C switch
A24 B9 Starter switch signal
A10 D4 Service check signal (Ignition timing adjusting connector)
A21 - K-Line
B21 D1 DTC memory voltage
C10 D6 VTEC oil pressure
A26 B8 Power steering pressure switch
A32 D2 Brake switch signal
C5 D9 Alternator FRsignal
C2 A16 Alternator control
C26 D13 ECT
A30 D10 ELD
C25 D15 IAT
- - PA
C27 D11 TPS
C23 B10 VSS
C28 D20 Sensor voltage
C18 D22 Sensor ground
C17 D17 MAP
C19 D19 Map sensor voltage
C7 D21 MAP sensor ground
C3 D3 Knock sensor



Wiring Conversions
http://www.hasport.com/Products/Wiring.htm
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Old 12-22-2003, 10:25 PM   #6 (permalink)
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VTEC switch point
http://hondata.com/techk20vtecswitchpoint.html

We are learning that the VTEC switch point is very important for the power curve.

In this example below of a K20A2 with CAI , we switched the VTEC point on at 5200 RPM instead of 5800. This provided a substantial gain in torque and power from 5800 to 6600 rpm - after the old VTEC switch point. The VTEC dip was minimised by switching just before a lowcam 5300 torque peak.

Why? We suspect that the airflow to the engine takes a while to reestablish after the VTEC switch point. The results speak well. About 10 ft/lb and 12 hp gain at 6000 rpm.
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Old 12-22-2003, 10:35 PM   #7 (permalink)
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Injector Wiring

High horsepower boosted cars often need large injectors. Most large capacity injectors are available in peak and hold form - about 2 ohms impedance, whereas most stock injectors from about 92 on are saturated (8-10 ohms impedance). Honda engine computers require a total injector impedance of about 10 ohms so a resistor pack is needed whenever the stock saturated injectors are swapped with peak and hold.

Early model injected Hondas; 90-95 Prelude and Accord; 89-91 JDM B16A Hondas all ran external resistor packs with low impedance injectors.


This wiring diagram shows the wiring for saturated (upper), and peak and hold injectors (lower). The engine computer activates the injectors by grounding each injector in turn.



Converting to Peak and Hold injectors

Near the brake master cylinder on OBD I cars is a connector that distributes power to the injectors and a number of sensors. Verify with a multimeter which wires go to the injectors. Cut all 4 and connect the wires coming from the injectors to the resistor pack. Connect the power wire from the resistor pack to all 4 of the unused wires coming from the power connector. OBD II cars may have this connector somewhere under the intake manifold.

Last edited by DOG; 09-07-2005 at 12:07 PM.
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