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Discussion Starter #1 (Edited)
Cell light staying on, bad computer? Also, Bad 02?

OK so I notice that my check engine light is on even when I put a jump wire for diagnose mode. I will turn the ignition to on and the check engine will stay on without blinking. Is my computer damage? I think that the last time that check for codes I left the paper clip in and I have seen turn on the car a few times, will this cause damage to the computer/diagnosis of the car? I already disconnected the battery and also the 7.5 fuse that supposed to erase any old codes, but even after this the check engine remains.

Another issue that I had was that I thought my 02 sensor was busted from being pinch between the down-pipe and the Intercooler piping, I think it broke the wires that connect to the 02 since the wire were connected but they just hanging to the side of the 02 instead of being nice and firm sticking up like they usually are.

I mention this cause after I took care of the leaks issue that I had with my car, my engine was running like butter, I could rev the engine without any issue and all the sudden it will turn on but if I try to rev the engine it will be all ruff and it turns off, Could it be the 02 being busted? I already change the location of the 02 so I don't have any contact issues, and also have a new 02 sensor on hand.
 

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Leaving the jumper in with the vehicle running will not harm anything. U jump the connector to set ignition timing with vehicle running right? So that shouldn't have an effect on the ecu.

What vehcile / obd is this. Iirc the ecu closes then ground circuit for the cel bulb. Possibly u have a short to ground for the bulb wire?
 

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A solid light when jumped means no codes are stored. Are you sure you have it jumped right?
 

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Discussion Starter #5
Its a 92 Hatch with a D16Z6 so that will make it an ODB1. I jump the wire and turn on the ignition (engine not running) to put my car in diagnosis mode.

I will check the ground and also the main relay.

The engine check light was on when my engine was running that's why I wanted to check for codes ( I was expecting a bad 02 sensor) for my diagnosis, instead I got a solid check engine light. If that means no code, why does it stay on when Im running the car? I disconnected the battery and even pull out the 7.5 fuse on the engine bay (this supposed to erased any previous code).

I'm following the procedure according to the manual, also check here and other sites as well as youtube tutorials and is telling me to do what I did so I'm pretty sure I'm doing it right, besides I have done it many times before with no problem.
 

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Discussion Starter #7
I will install the new 02 sensor, and go over everything. Not sure If I have another P28 I will swap the computer to see if that makes a difference, Can I use a P06 instead? In case I don't have the P28.

Being that my car is not tune yet, It should give me a code for the 02 regardless whether is working or not right? Like I mention before, the one that I have on the car right now I think is busted but I will try that one on my EX to see if is actually broken or not.
 

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I will install the new 02 sensor, and go over everything. Not sure If I have another P28 I will swap the computer to see if that makes a difference, Can I use a P06 instead? In case I don't have the P28.

Being that my car is not tune yet, It should give me a code for the 02 regardless whether is working or not right? Like I mention before, the one that I have on the car right now I think is busted but I will try that one on my EX to see if is actually broken or not.
You can try a P06, it wont harm anything using it. A tune doesn't affect rather or not the ECU will detect a malfunction with the o2. If you think the wires got messed up, then replace it. It's cheap insurance.
 

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Discussion Starter #10
I will swap the P28 with my DD to see whats going on, I already have a new 02 sensor but I will try it first without it to see if the 02 currently on the car still good, I rather use the money to get a new 02 for my wideband. Also will check my main relay, make sure everything is ok with that as well. Car was very low on gas so I will make sure I have at least 1/2 tank.
 

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Discussion Starter #11 (Edited)
OK what I did yesterday on my car, Install new 02 sensor, install new plugs, replace my distributor since the one I had on the car wasn't firing. Car now has half a tank. Check engine was still there.

Change the computer and install the one I thought was bad on my dd civic, car started perfect and no check engine was showing on my dd. Change cluster to see if that was wrong with my hatchback and check engine was still on using a different cluster.

Clean all the grounds on the car, check all the sensor plugs and seem to be OK. I have one question thou, I have a fitting where the original oil pressure sender unit is, one end goes to my oil pressure gauge inside cabin and the other one I re install the original sender unit but it is facing up now, would that make a difference? I know that if I unplug that sender unit for the oil pressure, the check engine light will stay on right? I'm thinking if the oil sending unit wire is bad or if the sender unit itself is bad, that will be a reason for the check engine light to be on all the time?

Don't know what else to do, any inputs???
 

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Does the car start? Any cut wires in the engine harness? Is it tucked?
 

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Discussion Starter #14
I know this will sound dumb but fuses and the ground on the thermostat housing. If the ecu is good your problem os in wiring
I clean all the grounds with a little metal brush, I clean both ends of the wire as well as the metal surface on the car, even use the wire brush on the bolts. Fuses on the engine bay i just went over with a check light and after touching each end in every fuse, the light came on so I figure they were good I guess. I will take each of them out one by one and see. Is there any fuse inside the cabin I should worry about? I will check my gauges connection to see if that's the problem.

Does the car start? Any cut wires in the engine harness? Is it tucked?
After I change the plugs and the distributor car started as usual and stayed running normally like it used to with no problem. I cut one wire for my tach, the blue wire near the brake booster and add it one wire pin to the computer harness to run to my boost selenoid
 

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That is correct if his CEL wasn't on without the service connector jumped.


FSM says code 0 = ECU
However, the first post is misleading. Is the CEL on without the jumper? He doesn't really say.

Boricuanolgy, to clarify. You said this:
"OK so I notice that my check engine light is on even when I put a jump wire for diagnose mode."

Your CEL is on with, AND without the service connector jumped correct? If so, refer to the FSM for code 0, if not HondaDNA is correct, and you have no codes.

"even when" makes me think you have a CEL with and without the jumper.
 

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Discussion Starter #16
That is correct if his CEL wasn't on without the service connector jumped.


FSM says code 0 = ECU
However, the first post is misleading. Is the CEL on without the jumper? He doesn't really say.

Boricuanolgy, to clarify. You said this:
"OK so I notice that my check engine light is on even when I put a jump wire for diagnose mode."

Your CEL is on with, AND without the service connector jumped correct? If so, refer to the FSM for code 0, if not HondaDNA is correct, and you have no codes.

"even when" makes me think you have a CEL with and without the jumper.
Ok guys first of all thanks for helping me out, I appreciate!!

To clarify everything, the issue that I have is that the check engine is solid ON with or without the jumper cable.

I disconnected the neg cable from the battery also took out the back up 7.5 fuse from the under hood relay/fuse box for 1 Minute, this should had erase any old engine codes right? If this is right that's the problem that I'm having that the light still Solid on after I do this.

My understanding is that it shouldn't be a check engine code save, it should be Zero codes. But if I start the engine and let it run, if there is something wrong then the check engine should come On and I should be able to know whats wrong with my car when I do a self diagnostic on the car but is not happening cause the check engine is solid On.

Hopes this clarify everything!!







Leaving the jumper in with the vehicle running will not harm anything. U jump the connector to set ignition timing with vehicle running right? So that shouldn't have an effect on the ecu.

What vehcile / obd is this. Iirc the ecu closes then ground circuit for the cel bulb. Possibly u have a short to ground for the bulb wire?
I believed that was the last thing I was doing when I left the jumper cable in, setting the ignition timing with the car running.

Can you elaborate on the Iirc ecu closing/short to ground for the bulb wire?


Check the capacitor in the ecu or the main relay. If not either of those maybe a bad transistor array
I will check with the main relay on my dd, Capacitor in the ecu? Bad transistor array? you got me with that one!!
 

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Discussion Starter #18
Well you said you took the ecu out and it ran a different car right? So the ecu is fine

The next step i would take would be to trace the power and ground wires to the ecu. Also a bad main relay would throw a solid cel.
I will swap main relay to see if that's the problem. Sorry for my stupidity but About tracing the power and ground, which one exactly? I already took care of all the engine grounds, are they others? And also when you mean power, which one are you talking about?

I put the "supposedly" bad ecu and swapped on my DD and it was OK, but I didn't took my good ecu and installed on my hatchback, would that make a difference?
 

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I'm going to fourth the possible short in the CEL signal wire.

The light gets power to one side when the key is in the run posistion. The ground comes from the ecu to turn it on.

You mentioned and intercooler so assuming it's an OBD1 ecu the CEL light output is A13 at the ecu.

Try this...unplug the ecu completely and turn the ingnition on. Does the CEL turn on? It shouldn't and if it does there's a short in the wire.
 
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