Updating the ECM/PCM

Known-Good PCM Substitution

Use the following procedure if you need a known-good ECM/PCM to test a vehicle. It allows you to swap an ECM/PCM from a "donor" vehicle without having to program it to the test vehicle's ignition key.
1. Cut a temporary ignition key for the test vehicle with a non-immobilizer key blank.
2. Remove the ECM/PCM from the test vehicle.
3. Write the test vehicle's VIN on the ECM/PCM you just removed to avoid confusing it with the donor vehicle's ECM/PCM.
4. Remove the known-good ECM/PCM from the donor vehicle, and install it in the test vehicle.




5. Tape the donor vehicle's ignition key head-to-head to the test vehicle's temporary key. The PCM will recognize the code from the donor vehicle's key and allow you to start the engine with the temporary key.




6. After completing your tests, reinstall both ECM/PCMs, and destroy the temporary key.
If the inspection for a particular code requires voltage or resistance checks at the ECM/PCM connectors, remove the right door sill molding. Pull the carpet back to expose the ECM/PCM. Unbolt the ECM/PCM cover, and connect the back probe sets and a digital multimeter as described below. Check the system according to the procedure described for the appropriate code(s).

How to Use the Backprobe Sets




Connect the backprobe adapters to the stacking patch cords, and connect the cords to a multimeter. Using the wire insulation as a guide for the contoured tip of the backprobe adapter, gently slide the tip into the connector from the wire side until it comes in contact with terminal end of the wire.




CAUTION:
- Puncturing the insulation on a wire can cause poor or intermittent electrical connections.
- Bring the tester probe into contact with the terminal from the terminal side of wire harness connectors in the engine compartment. For female connectors, lust touch lightly with the tester probe and do not insert the probe.