P0551
DTC P0551: Power Steering Pressure Switch Circuit Range/Performance
CIRCUIT OPERATION
- A battery positive voltage is applied to the power steering pressure switch output terminal (terminal No. 1) from the ECM (terminal No. 58) via the resistor in the ECM.
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 0 and 12 volts.
- While driving with the steering wheel held straight, the power steering pressure switch turns "OFF".
- The ECM checks whether the power steering pressure switch turns "OFF" or "ON" during driving.
DESCRIPTIONS OF MONITOR METHODS
Power steering pressure switch stays "ON" during specified go/stop operations.
MONITOR EXECUTION
Continuous
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
- Not applicable
Sensor (The sensor below is determined to be normal)
- Engine coolant temperature sensor
DTC SET CONDITIONS
Logic Flow Chart
Check Conditions
- Engine coolant temperature is higher than 20°C (68°F).
- Repeat 10 times or more: drive*1, stop*2.
Drive*1:
- Vehicle speed is more than 50 km/h (31 mph) lasting 4 seconds or more.
Stop*2:
- Vehicle speed is less than 1.5 km/h (1 mph).
Judgement Criterion
- 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.
- Connector damage.
- Harness damage.
- ECM failed.
DIAGNOSIS
Required Special Tools:
- MB991958: Scan tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
- MB992110: Power Plant ECU Check Harness
STEP 1. Using scan tool MB991958, check data list item 83: 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 83, Power Steering Pressure Switch.
- If the steering wheel is not turned while idling, "OFF" will be displayed.
- If the steering wheel is turned while idling, "ON" will be displayed.
(4)Turn
the ignition switch to the "LOCK" (OFF) position.
Q. Is the switch operating properly?
YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.
NO Go to Step 2.
STEP 2. Measure the power supply voltage at power steering pressure switch connector B-122 by backprobing.
(1)Do not disconnect the connector B-122.
(2)Start the engine and run at idle.
(3)Measure the voltage between terminal No. 1 and ground by backprobing.
- When steering wheel is not turned, voltage should be battery positive voltage.
- When steering wheel is turned, voltage should be 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-122 at power steering pressure switch and harness connector B-10 at ECM for damage.
Q. Is the harness connector in good condition?
YES Go to Step 4.
NO Repair or replace it. Harness Connector Inspection.
Then go to Step 9.
STEP 4. Using scan tool MB991958, check data list item 83: Power Steering Pressure Switch.
(1)Start the engine and run at idle.
(2)Set scan tool MB991958 to the data reading mode for item 83, Power Steering Pressure Switch.
- If the steering wheel is not turned while idling, "OFF" will be displayed.
- If the steering wheel is turned while idling, "ON" will be displayed.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
Q. Is the switch operating properly?
YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.
NO Replace the ECM. When the ECM is replaced, register the ID code. Refer to ID registration procedure manual - ID codes registration judgement table [Vehicles with KOS] or ID registration procedure manual - ID codes registration judgement table [Vehicles with WCM]. Then go to Step 9.
STEP 5. Check harness connector B-122 at power steering pressure switch and harness connector B-10 at ECM for damage.
Q. Is the harness connector in good condition?
YES Go to Step 6.
NO Repair or replace it. Harness Connector Inspection.
Then go to Step 9.
STEP 6. Check for harness damage between power steering pressure switch connector B-122 and ECM connector B-10.
(1)Disconnect the connector B-122 and B-10 measure at the harness side.
(2)Measure the resistance between connector B-122 (terminal No. 1) and connector B-10
(terminal No. 58).
- Should be less than 2 ohms.
Q. Is the measured resistance less than 2 ohms?
YES Then go to Step 7.
NO Repair it. Then go to Step 9.
STEP 7. Check for short circuit to ground between power steering pressure switch connector B-122 and ECM connector B-10.
(1)Disconnect the connector B-122 and B-10 measure at the harness side.
(2)Check for the continuity between connector B-122 (terminal No. 1) and ground.
- Not continuity.
Q. Is the harness wire in good condition?
YES Then go to Step 8.
NO Repair it. Then go to Step 9.
STEP 8. Replace the power steering pressure switch.
(1)Replace the power steering pressure switch.
(2)Check the trouble symptoms.
(3)Read in the diagnostic trouble code (DTC).
Q. Is DTC P0551 set?
YES Replace the ECM. When the ECM is replaced, register the ID code. Refer to ID registration procedure manual - ID codes registration judgement table [Vehicles with KOS] or ID registration procedure manual - ID codes registration judgement table [Vehicles with WCM]. Then go to Step 9.
NO Go to Step 9.
STEP 9. Using scan tool MB991958, check data list item 83: Power Steering Pressure Switch.
(1)Start the engine and run at idle.
(2)Set scan tool MB991958 to the data reading mode for item 83, Power Steering Pressure Switch.
- If the steering wheel is not turned while idling, "OFF" will be displayed.
- If the steering wheel is turned while idling, "ON" will be displayed.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
Q. Is the switch operating properly?
YES The inspection is complete.
NO Retry the troubleshooting.