Pinpoint Test D: Unusual Starter Noise

Starting System

Pinpoint Tests

Pinpoint Test D: Unusual Starter Noise

Normal Operation

Under normal operation, the Power Distribution Box (PDB) supplies constant power to the starter motor relay through fuse 13 (30A). When the key is placed in the START position, power is sent to the start diode through circuit CDC35 (BU/WH). Power continues through circuit CE336 (GN/WH) to the PCM and to the starter relay (TorqShift transmission) or the digital Transmission Range (TR) sensor (4R75 transmission). If the TR is in either the PARK or NEUTRAL position, power flows to the starter relay through circuit CET40 (GN/OG).

On vehicles equipped with a TorqShift transmission, the PCM will receive a signal from the transmission that the vehicle is in PARK or NEUTRAL through circuit VET32 (VT).

The PCM then provides ground on circuit CDC12 (YE) to the starter motor relay. The coil of the relay is energized and sends power to the starter motor on circuit CDC25 (BN/GN). The solenoid is grounded at the starter motor. Energizing the starter solenoid will engage the starter drive into the flexplate 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 rpm threshold, a set time has been exceeded or the ignition key 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 a remote starter switch between the starter motor solenoid terminals C197A-1, circuit 2037 (RD), and C197B-1, circuit 113 (YE/LB).




- Engage 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 Initial Inspection and Diagnostic Overview 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 ring gear for damaged or worn teeth.
- Is the noise due to ring gear tooth damage?

Yes
INSTALL a new flexplate. REFER to Removal and Replacement for 4.6L and 5.4L engines. REFER to Removal and Replacement for 6.8L engines. 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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