P0551
DTC P0551: Power Steering Pressure Sensor Circuit Range/PerformancePower Steering Pressure Switch Circuit:
CIRCUIT OPERATION
- A battery positive voltage is applied to the power steering pressure switch output terminal (terminal No. 1) from the ECM (terminal No. 37)
TECHNICAL DESCRIPTION
- The power steering pressure switch converts the existence of a power steering load into a high/low voltage, and inputs it into the ECM
- When the steering wheel is turned, hydraulic pressure rises. The power steering pressure switch closes, and the applied battery positive voltage will be grounded. With this, the power steering pressure switch output voltage will fluctuate between 12 volts and 0 volt.
- While driving with the steering wheel held straight, the power steering pressure switch turns "OFF".
- The ECM
DESCRIPTIONS OF MONITOR METHODS
- If the power steering pressure switch is constantly ON in spite of repeating the prescribed (stop-and-go) driving pattern, a malfunction is determined to have occurred.
MONITOR EXECUTION
- Continuous
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC stored in memory for the item monitored)
- Not applicable
Sensor (The sensor below is determined to be normal)
- Engine coolant temperature sensor
DTC SET CONDITIONS
Logic Flow Chart:
Logic Flowchart
Check Conditions
- Engine coolant temperature is higher than 18 °C (64 °F).
- Drive for 4 seconds or more with the vehicle speed is 50 km/h (31 mph) or more. Stop the vehicle [vehicle speed is 1.5 km/h (0.93 mph) or less]. Repeat 10 times or more.
Judgment Criteria
- Power steering pressure switch continues to be "ON".
OBD-II DRIVE CYCLE PATTERN
None.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Power steering pressure switch failed.
- Open or shorted power steering pressure switch circuit, or connector damage.
- ECM failed.
- PCM failed.
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991911: Main Harness B
STEP 1. Using scan tool MB991958, check data list item 27: Power Steering Pressure 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. Start the engine and run at idle.
3. Set scan tool MB991958 to the data reading mode for item 27, Power Steering Pressure Switch.
- If the steering wheel is stopped while idling, "OFF" will be displayed.
- If the steering wheel is steered while idling, "ON" will be displayed.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points.
NO: Go to Step 2.
STEP 2. Measure the power supply voltage at power steering pressure switch connector B-116 by backprobing.
1. Do not disconnect connector B-116.
2. Start the engine and run at idle.
3. Measure the voltage between terminal No. 1 and ground by backprobing.
- When steering wheel is stationary, voltage should measure battery positive voltage.
- When steering wheel is turned, voltage should measure 1 volt or less.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage within the specified range?
YES: Go to Step 3.
NO: Go to Step 5.
STEP 3. Check harness connector B-116 at power steering pressure switch for damage.
Q: Is the harness connector in good condition?
YES: Go to Step 4.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 4. Using scan tool MB991958, check data list item 27: Power Steering Pressure 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. Start the engine and run at idle.
3. Set scan tool MB991958 to the data reading mode for item 27, Power Steering Pressure Switch.
- If the steering wheel is stopped while idling, "OFF" will be displayed.
- If the steering wheel is steered while idling, "ON" will be displayed.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points.
NO: Replace the ECM or PCM. Then go to Step 14.
STEP 5. Check harness connector B-116 at power steering pressure switch for damage.
Q: Is the harness connector in good condition?
YES: Go to Step 6.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 6. Measure the power supply voltage at power steering pressure switch harness side connector B-116.
1. Disconnect connector B-116 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 1 and ground.
- Voltage should be battery positive voltage.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is battery positive voltage (approximately 12 volts) present?
YES: Go to Step 11.
NO: Go to Step 7.
STEP 7. Measure the power supply voltage at ECM connector C-119
1. Do not disconnect the ECM connector C-119
2. Disconnect the power steering pressure switch connector B-116.
3. Turn the ignition switch to the "ON" position.
4. Measure the voltage between terminal No. 37
- Voltage should be between battery positive voltage.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is battery positive voltage (approximately 12 volts) present?
YES: Go to Step 8.
NO: Go to Step 9.
STEP 8. Check harness connector C-119 at ECM
Q: Is the harness connector in good condition?
YES: Repair harness wire between power steering pressure switch connector B-116 (terminal No. 1) and ECM connector C-119 (terminal No. 37)
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 9. Check harness connector C-119 at ECM
Q: Is the harness connector in good condition?
YES: Go to Step 10.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 10. Check for short circuit to ground between power steering pressure switch connector B-116 (terminal No. 1) and ECM connector C-119 (terminal No. 37)
Q: Is the harness wire in good condition?
YES: Replace the ECM or PCM. Then go to Step 14.
NO: Repair it. Then go to Step 14.
STEP 11. Replace the power steering pressure switch.
1. Replace the power steering pressure switch.
2. Retest the system.
3. Check the diagnostic trouble code (DTC).
Q: Is DTC P0551 set?
YES: Go to Step 12.
NO: Go to Step 14.
STEP 12. Check harness connector C-119 at ECM
Q: Is the harness connector in good condition?
YES: Go to Step 13.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 13. Check for harness damage between power steering pressure switch connector B-116 (terminal No. 1) and ECM connector C-119 (terminal No. 37)
Q: Is the harness wire in good condition?
YES: Replace the ECM or PCM. Then go to Step 14.
NO: Repair it. Then go to Step 14.
STEP 14. Using scan tool MB991958, check data list item 27: Power Steering Pressure 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. Start the engine and run at idle.
3. Set scan tool MB991958 to the data reading mode for item 27, Power Steering Pressure Switch.
- If the steering wheel is stopped while idling, "OFF" will be displayed.
- If the steering wheel is steered while idling, "ON" will be displayed.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the switch operating properly?
YES: The procedure is complete.
NO: Repeat the troubleshooting.