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Riddle me this about the Check Engine Light...


Penglii

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OK, so the IP cluster in my TGP is totally functional except for all the usual ways... speedo/tach are off, boost gauge seems flaky, low fuel light flickers, etc.

However, all the lights and everything work correctly... and specifically, the Check Engine Light passes it's self diagnostic test via the Tech-1a.

This tells me that all the in-car wiring to the cluster is functioning fine.

 

I got another cluster, but I do not know if it is any more accurate or not. I plugged it into the car to test it and discover the check engine light will not illuminate under any condition, including the Tech-1 diagnostic.

 

I still don't know if the rest of the gauge works OK or not, because I immediately disconnected it and swapped the original back in. It powers up and everything, and the tach and boost and stuff all do their thing... but I did not check any accuracy.

 

According to the schematics, the Check Engine light gets it's signal from wires C15 & D5 from the IP harness.... so I get a logic probe out and test the bulb (working) and then the path from C15 to D5 (traces good). I hook up a small 9V battery to the bulb, and it illuminates.... so I put the bulb back and briefly connect the battery to C15 & D5... the Check Engine Light illuminates!

 

Something about this does not add up... it's too dark to check right now, but when I swap clusters again tomorrow is it magically going to work correctly this time?!

Or is there something I am failing to consider?

Edited by Penglii
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It did not illuminate with Key On - Engine Off (but the car's original cluster did and stiil does illuminate that way)... however I have not had a chance to re-install and see if it works all of a sudden.

 

I promise I will report back with my findings, hopefully I will have some free time tomorrow that I can use to find out. For all I know the bulb was loose and just needed re-inserting.

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It did not illuminate with Key On - Engine Off (but the car's original cluster did and stiil does illuminate that way)... however I have not had a chance to re-install and see if it works all of a sudden.

 

I promise I will report back with my findings, hopefully I will have some free time tomorrow that I can use to find out. For all I know the bulb was loose and just needed re-inserting.

 

Coooool deal, yea find out, could just be a loose circuit on the back of that cluster (or one of them..haha)

Let us know!

 

Also, skip the Tech1 and just do the jumper trick and see if you can't get it to illuminate giving you any sort of code (I beleive it will always at least give a code 32 which is a code for system pass/no faults)

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code 12, but yes, that indicates there are no serious and obvious faults in the ECM or PROM.

 

32 would be EGR :wink:

 

Haha, been a while since i coded an OBDI! Thanks for the correction :thumbsup:

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