I am guilty as charged. I have a Powertrain Control Module because my transmission is electronically controlled by the same module that controls my fuel injection. I didn't really swap the engine wiring harness. The wiring harness I am using was from a 94 and was VASTLY different. I completely stripped it down to wire and recreated each circuit one at a time. The PCM connectors were completely different for starters. Many circuits were similar or even the same and many were completely different or non existent. I have hours of testing in this harness to verify each circuit but I am not afraid to go over it again and again if necessary. My ICM is brand new and has been tested but I would never assume a new electrical component is functional until I have tested it myself.
Through some research I found out that in 91-92 They used QDRII which temporarily shut down and then reset if a device or its circuit shorts. Unlike QDR which are permanently damaged if a device or its circuit shorts because of no added circuit protection. I was not sure if my PCM had QDRII but you have informed me. Here is an explanation I want to post in case someone else reads this in the future. It could be vital for proper diagnosis and or understanding of these drivers.
Looking at the ECM and its quad drivers. Most ECM controlled devices are either solenoids or relays. Typically, solenoids are used for a circuit when the current draw is 0.75 amps or less, and relays are used in a circuit when the normal current draw is expected to exceed 0.75 amps. GM uses quad driver circuits inside the ECM to control the outputs to these devices. So quad drivers (QD) are integrated circuits inside the ECM that it uses to close or open the circuit path to ground, turning the device on or off. Depending on the make and model year GM vehicles use different variations of quad drivers.
Now lets look at testing quad driver devices and their circuits.
As we've all ready seen, most quad driver circuit faults are due to a short in a device or its circuit. (Wiring/connectors). However at times a device or circuit that is open will set a quad driver fault code.
Before replacing an ECM, always isolate the problem device or circuit. Replace the defective device or repair the circuit, and resets.
Each quad driver can control up to four devices. So diagrams will have to be used to find which devices the quad driver at fault is controlling.
Below is a typical diagram of QDM circuits. If this diagram was for quad driver B and that was the code that was set, we now know that this QDM controls, the TCC sol. Purge control sol. EGR control sol, and the check engine lamp.
A real diagram would list all circuit numbers, the wire colors, and connector terminal numbers. The important thing is that each device and circuit is tested, found to be good or repaired as necessary. The proper test on these circuits would be, with key off disconnect all ECM connectors, then with an amp meter set on the 10 amp scale connected to the control side of the circuit at the ECM connector and to ground turn the key on and check that the device turns on. With the device turned on, the meter should read 0.75 amps or less. Run this test for at least five minutes to make sure the device isn't overheating and shorting. The TCC solenoid cannot be tested in this manner in a vehicle that has a normally open third gear switch inside the transmission. A scanner thrtough an extended road test best checks the TCC circuit.
A normally operating device and its circuit will have at least 20 ohms of resistance and can be checked with an ohmmeter. This will tell if the circuit or device is open however, this will not place the device in operation. So if the device is only failing due to heat after being in use for a period of time the fault will not be found with a resistance test.
With the proper test equipment it's fairly easy to determine what circuit or device is causing a quad driver fault.
You will need a good digital multimeter and, if this first time buy the best would be one that has a 20 amp fused capability. The larger amp rating can come in handy when testing other electrical systems of your vehicle.
Also two 10 amp fused jumper wires keeping the in-line fuse as close to the power supply circuit as possible.
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