Exhaust Gas Temperature Sensor 4 -G648-, Checking

General Description

Exhaust gas temperature sensors are positive temperature coefficient (PTC) sensors. They measure the temperature of the exhaust gas. The Engine Control Module -J623- uses the signals from the exhaust gas temperature sensors to calculate the amount of contamination in the diesel particulate filter. They also protect the turbocharger from unacceptably high exhaust gas temperatures. The diesel particulate filter contamination status is calculated using these signals from the exhaust gas temperature sensors, together with the signals from; Differential Pressure Sensor -G505-, Mass Airflow Sensor -G70-, and the Oxygen Sensor 1 Before Catalytic Converter -GX10-. The signal from the exhaust gas temperature sensors also serves as component protection in order to protect the diesel particulate filter and turbocharger from excessively high exhaust gas temperatures as mentioned earlier.

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: SAFETY PRECAUTIONS .
View clean working conditions: CLEAN WORKING CONDITIONS .

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	IGNITION: OFF. DISCONNECT: Exhaust Gas Temperature Sensor 4 -G648- harness connector. CHECK: Exhaust Gas Temperature Sensor 4 -G648- component connector terminals 1 to 2 for resistance. SPECIFIED VALUE: 220 Ω (+/- 50 Ω @ approx. 20° C). -- Was Value obtained?	-- YES: GO TO: Step 3. -- NO: REPLACE: Exhaust Gas Temperature Sensor 4 -G648-. Refer to appropriate Service Information. GO TO: Step 4.
3	REMOVE: Engine Control Module - J623-. Refer to appropriate Service Information. CHECK: Exhaust Gas Temperature Sensor 4 -G648- harness connector terminal 1 to the Engine Control Module - J623- harness connector T105 / 55 for resistance. CHECK: Exhaust Gas Temperature Sensor 4 -G648- harness connector terminal 2 to the Engine Control Module - J623- harness connector T105 / 76 for resistance. SPECIFIED VALUE: 0.5 Ω (± 0.3 Ω). -- Were Values obtained?	-- YES: TIP: The Exhaust Gas Temperature Sensor 4 -G648- may fail under loaded operation; please swap a known good Exhaust Gas Temperature Sensor 4 -G648- prior to continuing to the next step. 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 4.
4	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.