Inspection Procedure 3: The TPMS Warning Light Does Not Illuminate As A Bulb Check For Three Seconds When the Ignition Switch

Inspection Procedure 3: The TPMS Warning Light does not Illuminate as a Bulb Check for Three Seconds when the Ignition Switch is Turned to the "ON" Position.











CIRCUIT OPERATION
For three seconds after the ignition switch is turned to the "ON" position, the TPMS receiver illuminates the TPMS warning light to check any breaks in the TPMS warning light circuit.

TECHNICAL DESCRIPTION (COMMENT)
If the TPMS warning light does not illuminate for three seconds when the ignition switch is turned to the "ON" position, diagnose the TPMS warning light signal circuit, power supply to the TPMS receiver, ignition signal, and/or ground circuit.

TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CASE:)
^ TPMS warning light signal harness wire (CAN-bus line) open circuit
^ Ignition signal harness wire of the TPMS receiver or battery power supply harness wire open circuit
^ Ground harness wire of the TPMS receiver open circuit
^ Malfunction of the combination meter
^ Malfunction of the TPMS receiver

DIAGNOSIS

Required Special Tool:
^ MB991223: Harness Set

STEP 1. Measure the voltage at C-121 TPMS receiver connector.





1) Disconnect TPMS receiver connector C-121, and check at the harness connector (component side).





2) Measure the voltage between terminal 5 and ground. It should measure battery positive voltage (approximately 12 volts).
3) Turn the ignition switch to the "ON" position.





4) Measure the voltage between terminal 10 and ground. It should measure battery positive voltage (approximately 12 volts).

Q: Is battery positive voltage (approximately 12 volts) present?
YES [all the measured voltages are equivalent to battery positive voltage]: Go to Step 6.
NO [voltage between terminal 5 and ground is not battery positive voltage]: Go to Step 2.
NO [voltage between terminal 10 and ground is not battery positive voltage]: Go to Step 4.

STEP 2. Check TPMS receiver connector C-121 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q: Is the TPMS receiver connector C-121 in good condition?
YES: Go to Step 3.
NO: Repair it. Then go to Step 12.

STEP 3. Check the wiring harness between TPMS receiver connector C-121 (terminal 5) and the battery.








NOTE: Also check intermediate connector C-24 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-24 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q: Is the wiring harness between TPMS receiver connector C-121 (terminal 5) and the battery in good condition?
YES: Repeat the troubleshooting from Step 1.
NO: Repair or replace it. Then go to Step 12.





STEP 4. Check TPMS receiver connector C-121 and junction block connector C-215 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q: Are TPMS receiver connector C-121 and junction block connector C-215 in good condition?
YES: Go to Step 5.
NO: Repair it. Then go to Step 12.





STEP 5. Check the wiring harness between TPMS receiver connector C-121 (terminal 10) and junction block connector C-215 (terminal 25).





Q: Is the wiring harness between TPMS receiver connector C-121 (terminal 10) and junction block connector C-215 (terminal 25) in good condition?
YES: Repeat the troubleshooting from Step 1.
NO: Repair or replace it. Then go to Step 12.





STEP 6. Check the wiring harness for open circuit.





1) Disconnect TPMS receiver connector C-121, and measure the resistance at the harness side.





2) Measure the resistance between terminal 6 and ground.
OK: Less than 2 ohms

Q: Is the check result normal?
YES: Go to Step 9.
NO: Go to Step 7.

STEP 7. Check TPMS receiver connector C-121 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q: Is TPMS receiver connector C-121 in good condition?
YES: Go to Step 8.
NO: Repair it. Then go to Step 12.

STEP 8. Check the wiring harness between TPMS receiver connector C-121 (terminal 6) and ground.





Q: Is the wiring harness between TPMS receiver connector C-121 (terminal 6) and ground in good condition?
YES: Return to Step 6.
NO: Repair or replace it. Then go to Step 12.

STEP 9. Check TPMS receiver connector C-121 and combination meter connector C-04 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q: Are TPMS receiver connector C-121 and combination meter connector C-04 in good condition?
YES: Go to Step 10.
NO: Repair it. Then go to Step 12.





STEP 10. Check the wiring harness between TPMS receiver connector C-121 (terminal 1 and 2) and combination meter connector C-04 (terminal 3 and 4).











NOTE: Also check joint connector C-03 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If joint connector C-03 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q: Is the wiring harness between TPMS receiver connector C-121 (terminal 1 and 2) and combination meter connector C-04 (terminal 3 and 4) in good condition?
YES: Replace the TPMS receiver and execute "Tire Pressure Sensor ID Registration" on scan tool MB991958 "Special Function". Then go to Step 11.
NO: Repair or replace it. Then go to Step 12.

STEP 11. Check the TPMS bulb check function.

Q: Turn the ignition switch to the "ON" position. Does the TPMS warning light illuminate for three seconds, and then go out?
YES: The procedure is complete.
NO: Replace the combination meter assembly. Then go to Step 12.

STEP 12. Retest the system.

Q: Turn the ignition switch to the "ON" position. Does the TPMS warning light illuminate for three seconds, and then go out?
YES: The procedure is complete.
NO: Repeat the troubleshooting from Step 1.