Motronic Engine Control Module Power Supply Relay - J271 -, CHECKING

General Description

The following procedure is used to diagnose the Motronic Engine Control Module Power Supply Relay -J271- and the Engine Control Module -J623- power supply voltage that is provided by the Motronic Engine Control Module Power Supply Relay -J271-.

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 concern.
2	IGNITION: OFF. DISCONNECT: Motronic Engine Control Module Power Supply Relay -J271-. IGNITION: ON. CHECK: Motronic Engine Control Module Power Supply Relay -J271- socket terminals 1 and 3 to ground for voltage. IGNITION: OFF. SPECIFIED VALUE: Battery voltage. -- Were Values obtained?	-- YES: GO TO: Step 3. -- 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.
3	REMOVE: Engine Control Module -J623-. Refer to appropriate Service Information. CONNECT: Jumper wire, between the Motronic Engine Control Module Power Supply Relay -J271- socket terminals 3 and 5. IGNITION: ON. CHECK: Engine Control Module -J623- harness connector T91 / 3, T91 / 5, and T91 / 6 to ground for voltage. IGNITION: OFF. SPECIFIED VALUE: Battery voltage. -- Were Values obtained?	-- YES: GO TO: Step 4. -- NO: GO TO: Step 5.
4	REMOVE: Jumper wire, between the Motronic Engine Control Module Power Supply Relay -J271- socket terminals 3 and 5. CHECK: Motronic Engine Control Module Power Supply Relay -J271- socket terminal 2 to the Engine Control Module -J623- harness connector T91 / 21 for resistance. SPECIFIED VALUE: 0.5 Ω (± 0.3 Ω) -- Was Value obtained?	-- YES: REPLACE: Motronic Engine Control Module Power Supply Relay -J271-. Refer to appropriate Service Information. GO TO: Step 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.
5	REMOVE: Jumper wire, between the Motronic Engine Control Module Power Supply Relay -J271- socket terminals 3 and 5. REMOVE: Fuse 14 (On Fuse Panel B) -SB14-. Refer to appropriate Service Information. CHECK: Downstream (output) side of Fuse 14 (On Fuse Panel B) -SB14- to the Engine Control Module -J623- harness connector T91 / 3, T91 / 5, and T91 / 6 for resistance. SPECIFIED VALUE: 0.5 Ω (± 0.3 Ω). -- Were Values obtained?	-- YES: REPLACE: Fuse Panel B -SB- fuse box. Refer to appropriate Service Information. GO TO: Step 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.
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 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 DTCs. If no DTC's return, the repair is complete. Return vehicle to Customer.