DTC 22
DTC 22: Stoplight Switch SystemStoplight Switch System Circuit Part 1:
Stoplight Switch System Circuit Part 2:
CIRCUIT OPERATION
- Battery positive voltage is supplied to the stoplight switch (terminal 2 and 3).
- When the brake pedal is depressed, battery positive voltage is applied to the ECM
DTC SET CONDITIONS
Check Condition
- The "CRUISE" indicator light illuminates.
Judgement Criteria
- Short in stop light switch circuit.
- Open circuit in the brake switch circuit (between ECM
TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CASE)
- Malfunction of the stoplight switch.
- Damaged harness or connector.
- Malfunction of the ECM
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A
- MB991223: Harness Set
- MB992006: Extra Fine Probe
- MB991923: Power Plant ECU Check Harness
STEP 1. Using scan tool MB991958, check data list item 74: Brake light switch.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Set scan tool MB991958 to data reading mode for auto-cruise control system.
- Item 74, Brake light switch.
- When the brake pedal is depressed, the display on scan tool MB991958 should be "ON".
- When the brake pedal is released, the display on scan tool MB991958 should be "OFF".
4. Turn the ignition switch to the "LOCK" (OFF) position.
5. Disconnect scan tool MB991958.
Q: Is the switch operating properly?
YES: Go to Step 14.
NO: Go to Step 2.
STEP 2. Check the stoplight operation.
Check the stoplight operation.
- When the brake pedal is depressed, the stoplight will illuminate.
- When the brake pedal is released, the stoplight does not illuminate.
Q: Dose the stoplight illuminate when the brake pedal is depressed and go out when the brake pedal is released?
YES: Go to Step 3.
NO: Go to Step 6.
STEP 3. Measure the terminal voltage at ECM
1. Disconnect all the connectors from the ECM
2. Connect special tool MB991923 between the ECM
3. Turn the ignition switch to the "ON" position.
4. Measure the terminal voltage between special tool 18-pin connector terminal 9 (ECM
- When the brake pedal is depressed, the voltage should measure battery positive voltage (approximately 12 volts).
- When the brake pedal is released, the voltage should measure 1 volt or less.
5. Turn the ignition switch to the "LOCK" (OFF) position.
6. Disconnect special tool MB991923 between the ECM
7. Reconnect all the connectors to the ECM
Q: Is the measured voltage battery positive voltage (approximately 12 volts) when the brake pedal is depressed and 1 volt or less when the brake pedal is released?
YES: Go to Step 13.
NO: Go to Step 4.
STEP 4. Check ECM
Q: Are the connectors and terminals in good condition?
YES: Go to Step 5.
NO: Repair or replace the damaged components. Then go to Step 22.
STEP 5. Check the harness wire between ECM
Q: Is the harness wire in good condition?
YES: Go to Step 13.
NO: Repair the damaged harness wire. Then go to Step 22.
STEP 6. Measure the power supply voltage at stoplight switch connector C-103 by backprobing.
1. Disconnect stoplight switch connector C-103.
2. Measure the power supply voltage between stoplight switch connector C-103 terminal 2 and ground.
3. Reconnect stoplight switch connector C-103.
Q: Is the measured voltage battery positive voltage (approximately 12 volts)?
YES: Go to Step 10.
NO: Go to Step 7.
STEP 7. Check stoplight switch connector C-103 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Are the connector and terminals in good condition?
YES: Go to Step 8.
NO: Repair or replace the damaged components. Then go to Step 22.
STEP 8. Check the harness wire between stoplight switch connector C-103 terminal 2 and fuse number 11 at the relay box at engine compartment for damage.
Q: Is the harness wire in good condition?
YES: Go to Step 9.
NO: Repair the damaged harness wire. Then go to Step 22.
STEP 9. Check the fuse number 11 at the relay box at engine compartment.
Q: Is the fuse in good condition?
YES: Go to Step 10.
NO: Check the stoplight system harness and replace the fuse. Then go to Step 22.
STEP 10. Check the stoplight switch.
1. Remove the stoplight switch.
2. Connect an ohmmeter to the stoplight switch between terminals 1 and 2.
3. Check for continuity between the terminals when the plunger of the stoplight switch is pushed in and when it is released.
4. The stoplight switch is operating properly if the circuit is open between terminals 1 and 2 when the plunger is pushed in to a depth of within 4.0 mm (0.16 inch) from the outer case edge surface, and if the resistance value is less than 2 Ohms between terminals 1 and 2 when it is released.
Q: Is the stoplight switch operating properly?
YES: Install the stoplight switch. Then go to Step 11.
NO: Replace the stoplight switch. Then go to Step 22.
STEP 11. Check stoplight switch connector C-103 and joint connector (1) C-28 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Are the connectors and terminals in good condition?
YES: Go to Step 12.
NO: Repair or replace the damaged components. Then go to Step 22.
STEP 12. Check the harness wire between stoplight switch connector C-103 terminal 1 and joint connector (1) C-28 terminal 12 for damage.
Q: Is the harness wire in good condition?
YES: Go to Step 13.
NO: Repair the damaged harness wire. Then go to Step 22.
STEP 13. Using scan tool MB991958, check data list item 74: Brake light switch.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Set scan tool MB991958 to data reading mode for auto-cruise control system.
- Item 74, Brake light switch.
- When the brake pedal is depressed, the display on scan tool MB991958 should be "ON".
- When the brake pedal is released, the display on scan tool MB991958 should be "OFF".
4. Turn the ignition switch to the "LOCK" (OFF) position.
5. Disconnect scan tool MB991958.
Q: Is the switch operating properly?
YES: Go to Step 21.
NO: Replace the ECM
STEP 14. Using scan tool MB991958, check data list item 89: Normally closed brake switch.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Set scan tool MB991958 to data reading mode for auto-cruise control system.
- Item 89, Normally closed brake switch.
- When the brake pedal is depressed, the display on scan tool MB991958 should be "ON".
- When the brake pedal is released, the display on scan tool MB991958 should be "OFF".
4. Turn the ignition switch to the "LOCK" (OFF) position.
5. Disconnect scan tool MB991958.
Q: Is the switch operating properly?
YES: Go to Step 21.
NO: Go to Step 15.
STEP 15. Measure the terminal voltage at ECM
1. Disconnect all the connectors from the ECM
2. Connect special tool MB991923 between the ECM
3. Turn the ignition switch to the "ON" position.
4. Measure the terminal voltage between special tool 23-pin connector (without red tape) terminal 33 (ECM
- When the brake pedal is depressed, the voltage should measure battery positive voltage (approximately 12 volts).
- When the brake pedal is released, the voltage should measure 1 volt or less.
5. Turn the ignition switch to the "LOCK" (OFF) position.
6. Disconnect special tool MB991923 between the ECM
7. Reconnect all the connectors to the ECM
Q: Is the measured voltage battery positive voltage (approximately 12 volts) when the brake pedal is depressed and 1 volt or less when the brake pedal is released?
YES: Go to Step 20.
NO: Go to Step 16.
STEP 16. Check the stoplight switch.
1. Remove the stoplight switch.
2. Connect an ohmmeter to the stoplight switch between terminals 3 and 4.
3. Check for continuity between the terminals when the plunger of the stoplight switch is pushed in and when it is released.
4. The stoplight switch is operating properly if the circuit is open between terminals 3 and 4 when the plunger is released, and if resistance value is less than 2 Ohms between terminals 3 and 4 when the plunger is pushed in to a depth of within 4.5 mm (0.18 inch) from the outer case edge surface.
Q: Is the stoplight switch operating properly?
YES: Install the stoplight switch. Then go to Step 17.
NO: Replace the stoplight switch. Then go to Step 22.
STEP 17. Check ECM
Q: Are the connectors and terminals in good condition?
YES: Go to Step 18.
NO: Repair or replace the damaged components. Then go to Step 22.
STEP 18. Check the harness wire between ECM
Q: Is the harness wire in good condition?
YES: Go to Step 19.
NO: Repair the damaged harness wire. Then go to Step 22.
STEP 19. Check the harness wire between stoplight switch connector C-103 terminal 4 and ground for damage.
Q: Is the harness wire in good condition?
YES: Go to Step 20.
NO: Repair the damaged harness wire. Then go to Step 22.
STEP 20. Using scan tool MB991958, check data list item 89: Normally closed brake switch.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Set scan tool MB991958 to data reading mode for auto-cruise control system.
- Item 89, Normally closed brake switch.
- When the brake pedal is depressed, the display on scan tool MB991958 should be "ON".
- When the brake pedal is released, the display on scan tool MB991958 should be "OFF".
4. Turn the ignition switch to the "LOCK" (OFF) position.
5. Disconnect scan tool MB991958.
Q: Is the switch operating properly?
YES: Go to Step 21.
NO: Replace the ECM
STEP 21. Read the diagnostic trouble codes.
Read the diagnostic trouble codes.
Q: Is DTC P22 set?
YES: Replace the ECM
NO: It can be assumed that this malfunction is intermittent.
STEP 22. Read the diagnostic trouble codes.
Read the diagnostic trouble codes.
Q: Is DTC P22 set?
YES: Return to Step 1.
NO: The procedure is complete.