DTC 29

DTC 29: Vehicle Speed Sensor System








Vehicle Speed Sensor System Circuit

CIRCUIT OPERATION
- 4.8 - 5.2 volt voltage is applied to the vehicle speed sensor output terminal (terminal 3) from the PCM (terminal 80). The vehicle speed sensor generates a pulse signal when the output terminal is opened and ground.
- The PCM compares the vehicle speed sensor signal to input shaft and output shaft speed sensor signals.
- If the vehicle speed sensor becomes inoperative, the transmission will not shift normally.

DTC SET CONDITIONS
If the PCM detects no pulse signal from the vehicle speed sensor for continuous period of 30 seconds under following conditions, it is judged as a vehicle sensor system malfunction and DTC number "29" is displayed.
- Driving forward
- Output shaft speed is 900 r/min or more

TROUBLESHOOTING HINTS (The most likely causes for this code to be set:)
- Malfunction of the vehicle speed sensor circuit
- Damaged harness, connector
- Malfunction of the PCM

DIAGNOSIS
Required Special Tool: MB991502: Scan Tool (MUT-II)

STEP 1. Check the speedometer.
Q: Is the speedometer operating properly?
YES: Go to Step 2.
NO: Check the vehicle speed sensor.





STEP 2. Using scan tool MB991502, check data list Item 29: Vehicle Speed Sensor.

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.

1. Connect scan tool MB991502 to the data link connector.
2. Start the engine.
3. Set scan tool MB991502 to data reading mode for item 29: Vehicle Speed Sensor. Check that the speedometer and MUT-II display speed match when driving at a vehicle speed of 40 km/h (25 mph).
4. Turn the ignition switch to "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: This malfunction is intermittent. Refer to "General Electrical Troubleshooting".
NO: Go to Step 3.

STEP 3. Using the oscilloscope, check the waveform at PCM connector C-41.





1. Do not disconnect connector C-41.





2. Connect an oscilloscope probe to PCM connector C-41 terminal 80 by backprobing.
3. Start the engine.





4. Check the waveform. The waveform should show a pattern similar to the illustration when running the vehicle.
5. Turn the ignition switch to "LOCK" (OFF) position.
Q: Is the waveform normal?
YES: Go to Step 5.
NO: Go to Step 4.








STEP 4. Check connectors C-41 at PCM and C-17 at Intermediate connector for damage.
Q: Are the connectors in good condition?
YES: Repair it because of harness open circuit or damage between PCM connector C-41 terminal 80 and intermediate connector C-17 terminal 3.
NO: Repair or replace it.





STEP 5. Check connector C-41 at PCM for damage.
Q: Is the connector in good condition?
YES: Go to Step 6.
NO: Repair or replace it.





STEP 6. Using scan tool MB991502, check data list item 29: Vehicle Speed Sensor.

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.

1. Connect scan tool MB991502 to the data link connector.
2. Start the engine.
3. Set scan tool MB991502 to data reading mode for item 29, Vehicle Speed Sensor. Check that the speedometer and MUT-II display speed match when driving at a vehicle speed of 40 km/h (25 mph).
4. Turn the ignition switch to "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: This malfunction is intermittent. Refer to "General Electrical Troubleshooting".
NO: Replace the PCM.