PCM Controlled Warning Lamps Diagnosis - Tachometer

Diagnostic Aids

For diagnosis of the instrument panel, perform the System Check in the Instrument Panel Cluster (IPC) Microprocessor.

Check for the following conditions:

^ Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
^ Damaged harness. Inspect the wiring harness for damage.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

3. Normally, ignition feed voltage should be present on the output driver circuit with the PCM disconnected and the ignition turned on.
4. Checks for a shorted component or a short to battery positive voltage on the output driver circuit. Either conditions would result in a measured current of over 0.5 amps.
5. Checks for a faulty instrument cluster.
14. A fault in the 24X/Camshaft position sensors feed or ground circuits will result in the loss of both PCM input pulses. Without a 24X reference pulse the PCM can not begin tachometer pulse control causing an inoperative tachometer.
16. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed. Refer to PCM Replacement/Programming.