P1769
DTC P1769: Stoplight Switch System
CIRCUIT OPERATION
- Battery positive voltage is supplied to the stoplight switch (terminal 2).
- When the brake pedal is depressed, battery positive voltage is applied to the PCM (terminal 9).
DTC SET CONDITIONS
If the stoplight switch is on for five minutes or more while driving above 50 km/h (31 mph), or all of the stop light bulbs are blown, it is judged there is a short circuit or open circuit in the stoplight switch. This causes DTC P1769 to be set.
TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CODE TO BE SET ARE:)
- Malfunction of the stoplight switch
- Malfunction of stoplight valve
- Damaged harness or connector
- Malfunction of the PCM
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
STEP 1. Check the brake pedal height.
Testing and Inspection.
Q. Is the height adjusted properly?
YES Go to Step 2.
NO Adjust the brake pedal to the proper height.
STEP 2. Check the stoplight valve.
Service and Repair.
Q. Is the stoplight valve in good condition?
YES Go to Step 3.
NO Replace the stoplight switch. Service and Repair.
STEP 3. Using scan tool MB991958, check data list item 19: Stoplight Switch.
(1)
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.
Connect scan tool MB991958 to the data link connector.
(2)Turn the ignition switch to the "ON" position.
(3)Set scan tool MB991958 to the data reading mode.
- Item 19: Stoplight Switch.
- When the brake pedal is depressed, the display on scan tool MB991958 should be "ON."
- When the brake pedal is not depressed, the display on scan tool MB991958 should be "OFF."
(4)Turn the ignition switch to the "LOCK" (OFF) position.
Q. Is the switch operating properly?
YES It can be assumed that this malfunction may be intermittent. How to Cope With Intermittent Malfunctions.
NO Go to Step 4.
STEP 4. Measure the stoplight switch power supply voltage at connector C-103 by backprobing.
(1)Remove the stoplight switch from the mounting bracket.
(2)Do not disconnect connector C-103.
(3)Measure the voltage between terminal 2 and ground by backprobing.
- The voltage should measure battery positive voltage.
Q. Is the measured voltage battery positive voltage?
YES Go to Step 7.
NO Go to step 5.
STEP 5. 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 6.
NO Repair or replace the damaged components. Harness Connector Inspection.
STEP 6. Check the harness for damage between stoplight switch connector C-103 terminal 2 and the power supply fuse.
Q. Is the harness wire in good condition?
YES Go to Step 7.
NO Repair or replace the harness wire.
STEP 7. Measure the stoplight switch output voltage to the PCM at connector C-103 by backprobing.
(1)Remove the stoplight switch from the mounting bracket.
(2)Do not disconnect connector C-103.
(3)Measure the voltage between terminal 1 and ground by backprobing.
- When the switch button is out (closed circuit), voltage should equal battery positive voltage.
- When the switch button is depressed (open circuit), voltage should measure less than 1.0 volt.
Q. Is the measured voltage battery positive voltage with the switch button released (closed circuit), and less than 1.0 volt with the switch button depressed (open circuit)?
YES Go to Step 9.
NO Go to Step 8.
STEP 8. Check the stoplight switch.
Testing and Inspection.
Q. Does the stoplight switch pass the checks?
YES Go to Step 9.
NO Replace the stoplight switch. Service and Repair.
STEP 9. Measure the stoplight switch output voltage at the PCM connector B-18 by using check harness special tool MB991923.
(1)Install the stoplight switch into the mounting bracket if it was removed.
(2)Disconnect all the connectors from the PCM.
(3)Connect special tool MB991923 (check harness) between the PCM and the body-side harness connector.
(4)Measure the voltage between terminal 9 and ground.
- When the brake pedal is depressed, voltage should measure battery positive voltage.
- When the brake pedal is not depressed, voltage should measure less than 1.0 volt.
Q. Is the measured voltage battery positive voltage with the brake pedal depressed (closed circuit), and less than 1.0 volt with the brake pedal released (open circuit)?
YES Go to Step 12.
NO Go to Step 10.
STEP10. Check PCM connector B-18 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 11.
NO Repair or replace the damaged components. Harness Connector Inspection.
STEP 11. Check the harness for damage between PCM connector B-18 terminal 9 and stoplight switch connector C-103 terminal 1.
Q. Is the harness wire in good condition?
YES Go to Step 12.
NO Repair or replace the harness wire.
STEP 12. Using scan tool MB991958, check data list item 19: Stoplight Switch.
(1)
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.
Connect scan tool MB991958 to the data link connector.
(2)Turn the ignition switch to the "ON" position.
(3)Set scan tool MB991958 to the data reading mode.
- Item 19: Stoplight Switch.
- When the brake pedal is depressed, the display on scan tool MB991958 should be "ON."
- When the brake pedal is not depressed, the display on scan tool MB991958 should be "OFF."
(4)Turn the ignition switch to the "LOCK" (OFF) position.
Q. Is the switch operating properly?
YES It can be assumed that this malfunction may be intermittent. How to Cope With Intermittent Malfunctions.
NO Replace the PCM. When the PCM is replaced, register the encrypted code. Encrypted Code Registration Criteria Table.