Engine Speed Sensor - G28-, Checking

General Description

The Engine Speed Sensor -G28- detects rpm and reference marks from a toothed wheel on the crankshaft. Without an engine speed signal, the engine will not start. If the engine speed signal fails while the engine is running, the engine will stop immediately.

Special tools and workshop equipment required

Multimeter.
Wiring Diagram.
Scan Tool.

Test requirements

Fuses OK.
Battery voltage OK.
Switch OFF all electrical and electronic accessories.
Vehicles with automatic transmission, ensure the selector lever position is in "P".
Vehicles with manual transmission, ensure the shifter lever position is in "N" with the parking brake applied.
Observe all safety precautions: .
View clean working conditions: .

Test Procedure

NOTE:

Note the CA1 and CMC both use the ECM connector T105a, and the CA2 uses the ECM connector T105b. Both connectors are identical except for the suffix of "a" or "b". For simplicity, please use the suffix "a".

Step	Procedure	Result / Action to Take
1	PERFORM: Preliminary Check to verify the customers complaint. Refer to . -- Was Complaint verified?	-- YES: GO TO: Step 2 Engine Speed Sensor - G28-, CHECKING - 2 . -- NO: GATHER more information from customer about the complaint.
2	IGNITION: OFF. CONNECT: Scan Tool. START or CRANK: Engine. CHECK: Engine rpm. SPECIFIED VALUE: Cranking or Idle rpm. IGNITION: OFF. -- Was Value obtained?	-- YES: CONDITION: May be intermittent. PERFORM: Visual Inspection of wiring and component. CHECK: Wiring for open, high resistance, short or harness connector for damage, corrosion, loose or broken terminals. REPAIR: Faulty wiring or connector. GO TO: Step 6 Engine Speed Sensor - G28-, CHECKING - 6 . -- NO: GO TO: Step 3 Engine Speed Sensor - G28-, CHECKING - 3 .
3	DISCONNECT: Engine Speed Sensor -G28- harness connector. IGNITION: ON. CHECK: Engine Speed Sensor -G28- harness connector terminals 1 to 3 for voltage. IGNITION: OFF. SPECIFIED VALUE: About 5.0 V. -- Was Value obtained?	-- YES: GO TO: Step 4 Engine Speed Sensor - G28-, CHECKING - 4 . -- NO: GO TO: Step 5 Engine Speed Sensor - G28-, CHECKING - 5 .
4	REMOVE: Engine Control Module - J623-. Refer to appropriate Service Information. CHECK: Engine Speed Sensor -G28- harness connector terminal 2 to the Engine Control Module - J623- harness connector T105a / 61 for resistance. SPECIFIED VALUE: 0.5 Ω (± 0.3 Ω). -- Was Value obtained?	-- YES: REMOVE: Engine Speed Sensor -G28-. Refer to appropriate Service Information. CHECK: Engine Speed Sensor -G28- sensor wheel for proper seating, damage and/or run - out. Refer to appropriate Service Information. Sensor wheel OK. REPLACE: Engine Speed Sensor -G28-. Refer to appropriate Service Information. GO TO: Step 6 Engine Speed Sensor - G28-, CHECKING - 6 . -- NO: PERFORM: Visual Inspection of wiring and component. CHECK: Wiring for open, high resistance, short or harness connector for damage, corrosion, loose or broken terminals. REPAIR: Faulty wiring or connector. GO TO: Step 6 Engine Speed Sensor - G28-, CHECKING - 6 .
5	REMOVE: Engine Control Module - J623-. Refer to appropriate Service Information. CHECK: Engine Speed Sensor -G28- harness connector terminal 1 to the Engine Control Module - J623- harness connector T105a / 69 for resistance. CHECK: Engine Speed Sensor -G28- harness connector terminal 3 to the Engine Control Module - J623- harness connector T105a / 60 for resistance. SPECIFIED VALUE: 0.5 Ω (± 0.3 Ω). -- Were Values obtained?	-- YES: GO TO: Step 6 Engine Speed Sensor - G28-, CHECKING - 6 . -- NO: PERFORM: Visual Inspection of wiring and component. CHECK: Wiring for open, high resistance, short or harness connector for damage, corrosion, loose or broken terminals. REPAIR: Faulty wiring or connector. GO TO: Step 6 Engine Speed Sensor - G28-, CHECKING - 6 .
6	Final Procedure Perform a road test to verify repair. -- Does the original DTC return?	-- YES: CHECK: Engine Control Module -J623- harness connector for any damaged, pushed-out pins. REPAIR: As necessary. If all electrical connections are OK: REPLACE: Engine Control Module -J623-. Refer to appropriate Service Information. Clear the DTC's. Refer to . Repair is complete. Generate Readiness Code. Refer to . Return vehicle to Customer. -- NO: Perform the diagnostic procedure for any DTC's. If no DTC's return, the repair is complete. Return vehicle to customer.