Check Engine light on

EDAVE12

MEMBER
1992 ISUZU BIGHORN
270,000 MILES

I have a V6 petrol Bighorn and 75% of the time I use it the Check Engine light comes. It stays illuminated as long as have the foot on the accelerator and goes out when coasting. There is no noticable affect on the running performance when light is on. I have tried to get a diagnostic code flashed (OBD1) but it flashes the code for no fault found.

This happens after about 20 minutes of driving which made me initially think it was a problem with the O2 sensor. Apparently this could happen with unheated sensor models as the sensor is locked out by the ECU until the exhaust is up to temperature, but I think I have a heated verson.

Any clues

5 Replies

SATURNTECH9

MECHANIC
30,870 POSTS

Have you tried using a scan tool to read the codes?From when the light turns on code be a egr issue.

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Tuesday, October 9th, 2012 AT 11:59 PM

KHLOW2008

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Maybe manual retrieval of the trouble codes might show something.

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Wednesday, October 10th, 2012 AT 2:27 AM

KHLOW2008

MECHANIC
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Sorry, I meant to say if it does not show anything, you can leave the system in diagnostic mode and go for a test drive till the light shows. It might show something.

Alternatively, check for a bad ground circuit for the ECM.

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Wednesday, October 10th, 2012 AT 2:29 AM

EDAVE12

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2 POSTS

Running in the diagnostic mode, had thought of doing that so will give it a go. The other thought was since the light goes out when coasting to a stop may be why no fault codes show up. I might try hitting the throttle before stopping so the light is on then turn the engine off, hopefully the light will come on and I will get a fail code.
Will let you know how we go.

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Wednesday, October 10th, 2012 AT 10:21 AM

KHLOW2008