LSxTune.com

LSxTune Original Articles and Writings #1

1. How do I remove my PCM? October 08, 2008

PCM Removal

The subject of this writing is removal and reinstallation of the PCM from a 1998-2002 LS1 F-body.

1. Disconnect the car’s positive battery cable. Do not forget to do this first.
2. Now it is time to remove the PCM’s harnesses. The harnesses are bolted to the PCM with a 7mm bolt through the center of each. These bolts are labeled “A” in the image. Loosen the 7mm bolts until the harness connectors can be pulled from the PCM. Fold the ends of the harness back and out of your way.
3. Remove the plastic ‘basket’ that the PCM is held in. This basket is bolted down to the inner fender with two 10mm bolts. These bolts are labeled “B” in the image. Once removed, the PCM and basket can be maneuvered around and removed from beneath the cowl.
4. Slide the PCM out of the black plastic basket.

Reinstallation is basically reverse order, and it goes like this:

1. Make sure that the battery is [still] disconnected. Slide the PCM back into it’s back plastic housing.
2. Work the PCM and basket back into the fender under the cowl and replace the two 10mm bolts that secure the basket to the inner fender. These are the bolts labeled B in the image.
3. Replace the ends of the harness onto the PCM’s connector side. They can only go on one side and in one direction. Be very careful and conscious when tightening the connectors back down with their 7mm hardware (again, labeled “A” in the image) and just tighten them snug. Avoid over tightening the connectors as this can lead to pins that make poor contact. This can cause very troublesome intermittent issues.
4. Reconnect the positive battery cable.

Some notes related to battery disconnection: The PCM’s programming is in non-volatile areas (will NOT be affected by power removal) but items like codes (DTC’s) and the status of internal emissions readiness tests, learned fuel trim profiles, and learned idle airflow needs are stored in an area that is wiped clean when power is removed. On re-installation of your PCM, during the first few drive cycles, the computer will be relearning fuel and airflow adjustments specific to your setup. If it acts a little funny at first re-start, this is why, and it could take a short drive time to straighten itself out.