DTC 38

DTC 38: Stoplight Switch System

Part 1 Of 2:

Part 2 Of 2:

CIRCUIT OPERATION
^ The ON signal when the brake pedal is pressed or the OFF signal when the brake pedal is released is input to the ABS-ECU (terminal 14).

ABS DTC SET CONDITION
Output is provided in the following cases:
^ Stoplight switch is not operating properly and remains in ON state for more than 15 minutes.
^ Stoplight switch system harness is damaged and no signal is input to ABS-ECU.

TROUBLESHOOTING HINTS (The most likely causes for this DTC is to set are:)
^ Malfunction of the stoplight switch
^ Damaged wiring harness or connector
^ Malfunction of the hydraulic unit (integrated with ABS-ECU)

DIAGNOSIS

Required Special Tools:
^ MB991223: Harness Set
^ MB991958: Scan Tool (MUT-III Sub Assembly)
^ MB991824: Vehicle Communication Interface
^ MB991827: MUT-III USB Cable
^ MB991911: MUT-III Main Harness B
^ MB991529: Diagnostic Trouble Code Check Harness

STEP 1. Check the stoplight operation.
Q: Does the stoplight light or go out correctly?
YES: Go to Step 3.
NO: Go to Step 2.

STEP 2. Check the stoplight switch installation condition.
Q: Is the stoplight switch installed properly?
YES: Go to Step 4.
NO: Install it correctly and then go to Step 7.

STEP 3. Check the stoplight switch circuit at the ABS-ECU connector A-02.
1. Disconnect the ABS-ECU connector A-02 and measure at the harness side.
2. Press the brake pedal. (The stoplight switch is turned to ON.)
3. Measure the voltage between terminal 14 and ground.





Q: Is the voltage approximately 12 volts (battery positive voltage)?
YES: Replace the hydraulic unit (integrated with ABS-ECU) and then go to Step 7.
NO: Go to Step 5.

STEP 4. Check the stoplight switch continuity.
1. Remove the stoplight switch.





2. Connect an ohmmeter to the stoplight switch terminals 1 and 2, and check whether there is continuity when the plunger of the stoplight switch is pushed in and when it is released.





3. The stoplight switch is in good condition if there is no continuity when the plunger is pushed in to a depth of within 4 mm (0.2 inch) from the outer case edge surface, and if there is continuity when it is released.
Q: Is the stoplight switch damaged?
YES: Replace it and then go to Step 7.
NO: Go to Step 6.

STEP 5. Check the harness wire between the ABS-ECU connector A-02 (terminal 14) and the stoplight switch connector C-03 (terminal 1).





NOTE: After inspecting the intermediate connector C-06, inspect the wire. If the intermediate connector C-06 is damaged, repair or replace it. If the connector has been repaired or replaced, go to Step 7.








Q: Is the harness wire between the ABS-ECU connector A-02 (terminal 14) and the stoplight switch connector C-03 (terminal 1) damaged?
YES: Repair it and then go to Step 7.
NO: No action is to be taken.

STEP 6. Check the harness wire between relay box fuse number 11 and stoplight switch connector C-03 (terminal 2).








Q: Is the harness wire between the relay box fuse number 11 and the stoplight switch connector C-03 (terminal 2) damaged?
YES: Repair it and then go to Step 7.
NO: Check and repair the harness wire between stoplight switch and stoplight. Then go to Step 7.

STEP 7. Recheck for diagnostic trouble code.
Q: Does the diagnostic trouble code 38 reset?
YES: Return to Step 1.
NO: This diagnosis is complete.