Quote:
Originally Posted by Blue Bowtie
The quad drivers are hardware in the ECM, not the PROM or MEMCAL pack. A quad driver is an array of solid state output switches (four of them in a package) used to operate moderate load devices, such as the EGR solenoid, EVAP, indicator lights, transmission solenoids, etc. The ECM monitors them to see if they have overloads or open circuits. When the ECM detects a fault it sets a code. That can mean a failed driver in the ECM, or an open or shorted circuit or device connected to a driver.
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I'm barking up the right tree
I need a schematic or diagram that indicates wire colors, pin locations in the ECM connectors, and reference voltages so I can start narrowing things down. I can check ref voltage at the sensors and solenoids to check for short to ground or opens but need to know where to find them at the junction blocks, the ECM and it's connectors etc.. My manual doesn't cover 1993 TSport with the 3.8L engine. I assume the wiring will be different enough on the '91-'92 3.1L to let me down?
If the Qdrivers monitor the indicator lights, might a bad coolant temp gauge trip a code (or is that independant of the ECM circuits)? The temp gauge needle rides on 1/4 max; I've changed out that coolant temperature sensor, and I've replaced the thermostat with a 195F. It made no diff to the gauge; the needle never reaches up past the 1/4 position.
I found this link on YouTube. It is just about all I need except I would like a diagram to reference along with it.
Watch "How to test an electronic EGR valve (GM P1406 case study)" on YouTube
https://youtu.be/te_kapz-fj4
This guy ScannerDanner has a bunch of diagnostic videos on his YouTube channel, and a forum. He is teaming with info; talks a litte fast but it sinks in when reviewed. Fun to watch too.
Does the 93 TSport with 3.8L have an EVAP Vent Solenoid as well as the purge valve solenoid, or does one do the same job as the other?