Automatic Glow Time Control Module -J179- AND GLOW PLUGS, CHECKING

General Description

The glow plugs are activated by the Engine Control Module -J623- through the Automatic Glow Time Control Module -J179-. The voltage on the individual glow plugs is adjusted over the frequency of the PWM impulses. For quick start with an ambient temperature of less than 64° F (18° C), a maximum voltage of 11.5 volts is present during preheating. This ensures that the glow plug heats up as quickly as possible (maximum two seconds) to over 1, 832° F (1, 000° C), thus reducing the preheating time of the engine. Post-heating is performed up to a coolant temperature of 64° F (18° C) after engine start for a maximum of five minutes. Post-heating helps reduce hydrocarbon emissions and combustion noise during the engine warm-up phase.

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 Auto. Transmission, ensure Selector Lever position is in "P".
Vehicles with Man. Transmission, ensure Shifter Lever position is in "N" with Parking Brake applied.
Coolant Temperature: < 18° C.
Observe all safety precautions: SAFETY PRECAUTIONS .
View clean working conditions: CLEAN WORKING CONDITIONS .
For Hybrid vehicles refer to: HIGH VOLTAGE SYSTEM GENERAL WARNINGS .

NOTE:

The Glow Plug terminal / connector is not repairable. The harness must be replaced if damaged.

Test Procedure

Step	Procedure	Result / Action to Take
1	PERFORM: Preliminary Check to verify the customers complaint. Refer to PRELIMINARY CHECK . -- Was Complaint verified?	-- YES: GO TO: Step 2. -- NO: GATHER more information from customer about the complaint.
2	Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY . -- Are there fault codes present for the Glow Plugs -- ?	-- YES: GO TO: Step 5. -- NO: GO TO: Step 3.
3	IGNITION: OFF. DISCONNECT: Automatic Glow Time Control Module -J179- harness connector. IGNITION: ON. CHECK: Automatic Glow Time Control Module -J179- harness connector terminals 6 and 11 to ground for voltage. CHECK: Automatic Glow Time Control Module -J179- harness connector terminal 7 to Battery voltage for voltage. SPECIFIED VALUE: Battery voltage. IGNITION: OFF. -- Were Values obtained?	-- YES: GO TO: Step 4. -- 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 7.
4	CHECK: Automatic Glow Time Control Module -J179- harness connector terminal 9 to Engine Control Module -J623- harness connector T91 / 77 for resistance. CHECK: Automatic Glow Time Control Module -J179- harness connector terminal 10 to Engine Control Module -J623- harness connector T91 / 55 for resistance. SPECIFIED VALUE: 0.5 Ω (+/- 0.3 Ω). -- Were Values obtained?	-- YES: REPLACE: Automatic Glow Time Control Module -J179-. Refer to appropriate Service Information. GO TO: Step 7. -- 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 7.
5	IGNITION: OFF. DISCONNECT: Automatic Glow Time Control Module -J179- harness connector. DISCONNECT: Suspect Glow Plug -- harness connector (per DTC stored). CHECK: The suspect Glow Plug -- (per DTC stored) component connector terminal x to ground for resistance (refer to the appropriate wiring diagram for terminal and connector location). SPECIFIED VALUE: 1.3 Ω (+/- 0.3 Ω @ 20° C). -- Was Value obtained?	-- YES: GO TO: Step 6. -- NO: REPLACE: The Glow Plug --. Refer to appropriate Service Information. GO TO: Step 7.
6	CHECK: Automatic Glow Time Control Module -J179- harness connector terminal x to suspect Glow Plug -- harness connector terminal x for resistance (refer to the appropriate wiring diagram for terminal and connector location). SPECIFIED VALUE: 0.5 Ω (+/- 0.3 Ω). -- Was Value obtained?	-- YES: TIP: The Glow Plug -- may fail under loaded operation; please swap a known good Glow Plug -- prior to continuing to the next step. GO TO: Step 7. -- 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 7.
7	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 DIAGNOSTIC MODE 04 - ERASE DTC MEMORY . Repair is complete. Generate Readiness Code. Refer to READINESS CODE . 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.