Inspection Procedure 4: Steering Wheel Sensor Power Supply Circuit System

INSPECTION PROCEDURE 4: Steering wheel sensor power supply circuit system








CIRCUIT OPERATION
^ The steering wheel sensor is energized by the ignition switch (IG1) through multi-purpose fuse 2 and the steering wheel sensor terminal 2.
^ If the power supply to the steering wheel sensor has failed, scan tool (M.U.T.-III Sub Assembly) will not be able to communicate with it.

TROUBLESHOOTING HINTS (The most likely causes for this case:)
^ Damaged wiring harness or connector
^ Defective battery
^ Charging system failed
^ Malfunction of the steering wheel sensor

DIAGNOSIS

Required Special Tools:
^ MB991958: Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: Vehicle Communication Interface (V.C.I.)
^ MB991827: M.U.T.-III USB Cable
^ MB991910: M.U.T.-III Main Harness A
^ MB991997: ASC Check Harness

STEP 1. Measure the voltage at steering wheel sensor connector C-312.





1) Disconnect the connector C-312.
2) Turn the ignition switch to the "ON" position.
3) Measure the voltage between terminal 2 and ground. It should measure approximately 12 volts (battery positive voltage).
Q: Is battery positive voltage (approximately 12 volts) present?
YES: Go to Step 3.
NO: Go to Step 2.

STEP 2. Check the following connectors.





^ Joint connectors (2) C-01





^ Junction block connectors C-202 and C-215





^ Ignition switch connector C-308





^ Steering wheel sensor connector C-312
Check the connectors, for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Are the connectors and terminals in good condition?
YES: An open or short circuit may be present in the power supply line to the steering wheel sensor. Repair the wiring harness between steering wheel sensor connector C-312 terminal 2 and ignition switch connector C-308 terminal 4. Go to Step 8.
NO: Repair or replace the damaged component(s). Then go to Step 8.

STEP 3. Measure the resistance at steering wheel sensor connector C-312.





1) Disconnect the steering sensor connector C312, and measure at the harness side connector.
2) Measure the resistance between terminal 5 and body ground.
Q: Is the measured resistance 2 ohms or less?
YES: Go to Step 5.
NO: Go to Step 4.

STEP 4. Check steering wheel sensor connector C-312 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q: Are the connectors and terminals in good condition?
YES: An open circuit may be present in the ground circuit. Repair the wiring harness between steering wheel sensor connector C-312 terminals 5 and the body ground. Then go to Step 8.
NO: Repair or replace the damaged component(s). Then go to Step 8.

STEP 5. Check the battery.
Check the battery.
Q: Is the battery in good condition?
YES: Go to Step 6.
NO: Charge or replace the battery. Then go to Step 8.

STEP 6. Check the charging system.
Check the charging system.
Q: Is the charging system in good condition?
YES: Go to Step 7.
NO: Repair or replace the charging system component(s). Then go to Step 8.

STEP 7. Retest the system.
Q: Can the steering wheel sensor communicate with the scan tool (M.U.T.-III Sub Assembly)?
YES: It can be assumed that this malfunction is intermittent.
NO: Replace the steering wheel sensor. Then go to Step 8.

STEP 8. Retest the system.
Q: Can the steering wheel sensor communicate with the scan tool (M.U.T.-III Sub Assembly)?
YES: The procedure is complete.
NO: Go to Step 1.