DTC 51

CIRCUIT DESCRIPTION:

Code 51 sets if any one of the following occur:
^ Faulty PROM unit.
^ PROM unit improperly installed (may not set a code if installed backwards).
^ Some PROM pins not making contact (i.e., bent).

Always check to see that the PROM pins are not bent and are inserted properly into the ECM. Make certain the PROM is installed in the proper direction.

NOTE: When installing a service replacement ECM, the use of incorrect PROM installation procedures, may cause the ECM to fail before it can be installed in the vehicle. This condition may appear as if the ECM were defective when it was shipped to the dealership, when in fact it was damaged while being installed. This condition may also occur when installing a new PROM in the original ECM. Excessive vertical force applied to the PROM may result in flexing of the circuit board and damage to the connections between the circuit board and attached components. Excessive force may result from incorrect PROM installation procedures or from interference between the PROM and the access cover. To avoid this problem condition, use the following installation procedure.

1. Inspect the PROM. If a cork spacer is found glued to it, remove the spacer prior to installation.

2. Align small notches with matching notches in the PROM socket inside the ECM.

3. VERY GENTLY press down on the ends of the PROM until the locking levers are rotated toward the sides of the PROM. DO NOT press down until the locking levers SNAP into place. Use only enough force to engage the PROM into its socket.

4. While continuing light pressure on the ends of the PROM, use your index fingers to press the locking levers inward until they "snap" into place. Listen for click.

5. Install PROM access cover and install ECM in vehicle.