Pinpoint Test D: Unusual Starter Noise

Starting System

Pinpoint Tests

Pinpoint Test D: Unusual Starter Noise

Normal Operation

Under normal operation, when the ignition switch is turned to the START position and released, the PCM receives a starter motor request signal through circuit CDC35 (BU/WH), power is then supplied to the starter relay through circuit CDC38 (WH/VT) from the PCM. The PCM will receive a signal from the transmission that the vehicle is in PARK or NEUTRAL through circuit CET40 (GN/OG). A ground is supplied through circuit CDC12 (YE) from the PCM causing the starter relay coil to energize and the relay contacts close. This allows power to be supplied from Battery Junction Box (BJB) fuse 13 (30A) to the relay contacts which then flows through circuit CDC25 (BN/GN) to the starter solenoid. The solenoid is grounded at the starter motor. Energizing the starter solenoid will engage the starter drive into the ring gear and closes the solenoid contacts allowing power directly from the battery through circuit SDC02 (RD) to the starter motor to start the engine. The PCM will disengage the starter motor based on engine running (rpm threshold), a set crank time has been exceeded or the ignition switch has been turned to the OFF position.

This pinpoint test is intended to diagnose the following:
- Starter motor mounting
- Starter motor mounting bolts
- Starter motor drive
- Flywheel or flexplate ring gear
- Starter motor

PINPOINT TEST D: UNUSUAL STARTER NOISE

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D1 CHECK THE STARTER MOTOR MOUNTING


- Inspect the starter motor mounting bolts for looseness.
- Is the starter motor mounted correctly?

Yes
GO to D2.

No
REINSTALL the starter motor correctly. REFER to Starter Motor Service and Repair.

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D2 CHECK FOR ENGINE NOISE


- Ignition OFF.
- Connect one end of a fused jumper wire to starter motor solenoid C197B-1, circuit CDC25 (BN/GN). Momentarily connect the other end of the jumper to starter motor C197A-1, circuit SDC02 (RD), engaging the starter motor and verify that the noise is due to the starter operation.




- Is the noise due to the starter motor engagement?

Yes
GO to D3.

No
REFER to Engine System - General Information Testing and Inspection to continue the diagnosis.

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D3 CHECK FOR UNUSUAL WEAR


- Remove the starter motor. Refer to Starter Motor Service and Repair.
- Inspect the flexplate for damaged or worn teeth.
- Is the noise due to flexplate damage?

Yes
INSTALL a new flexplate. REFER to Engine - 5.4L (3V) Removal and Replacement. EXAMINE the starter pinion teeth. If damaged, INSTALL a new starter motor. REFER to Starter Motor Service and Repair. TEST the system for normal operation.

No
INSTALL a new starter motor. REFER to Starter Motor Service and Repair. TEST the system for normal operation.

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