Code No. P0551: Power Steering Fluid Pressure Sensor System

CONDITION

A power voltage of 5 V is applied to power steering fluid pressure sensor (terminal No. 3) from the engine-ECU <M/T> or engine-A/T-ECU <A/T> (terminal No. 97).
The power voltage is earthed to the engine-ECU <M/T> or engine-A/T-ECU <A/T> (terminal No. 96) from the power steering fluid pressure sensor (terminal No. 1).
The sensor signal is inputted to the engine-ECU <M/T> or engine-A/T-ECU <A/T> (terminal No. 84) from power steering fluid pressure sensor output terminal (terminal No. 2).

FUNCTION

Detect the power steering oil pump load caused by the steering and input it into engine-ECU <M/T> or engine-A/T-ECU <A/T>. Engine-ECU <M/T> or engine-A/T-ECU <A/T> determines the power steering oil pump load through power steering fluid pressure sensor to perform the idle up control depending on the load.

TROUBLE JUDGMENT

Check Condition

All the time after the microcomputer start.

Judgment Criteria

Power steering fluid pressure sensor output voltage has continued to be 4.8 V or more for 5 seconds.

Power steering fluid pressure sensor output voltage has continued to be 0.2 V or less for 5 seconds.

PROBABLE CAUSE

Failed power steering fluid pressure sensor
Failed power steering
Open/short circuit in power steering fluid pressure sensor circuit or loose contact.
Failed engine-ECU <M/T>
Failed engine-A/T-ECU <A/T>

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III data list

Refer to Data List Reference Table

Item B4: Power steering fluid pressure sensor

Q. Is the check result normal?

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points)

	Go to Step 2 .

STEP 2. Check for stationary steering effort (Refer to ).

Q. Is the check result normal?

	Go to Step 3 .

	Repair.

STEP 3. Connector check: B-20 power steering fluid pressure sensor connector

Q. Is the check result normal?

Go to Step 4 .

Repair or replace.

STEP 4. Perform voltage measurement at B-20 power steering fluid pressure sensor connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No.3 and earth.

OK: 4.9 - 5.1V

Q. Is the check result normal?

Go to Step 10 .

Go to Step 5 .

STEP 5. Perform voltage measurement at C-113 engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector.

Measure engine-ECU <M/T> or engine-A/T-ECU <A/T> terminal voltage.

Ignition switch: ON

Voltage between terminal No.97 and earth.

OK: 4.9 - 5.1V

Q. Is the check result normal?

Go to Step 6 .

Go to Step 7

STEP 6. Connector check: C-113 engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector

Q. Is the check result normal?

Check power supply line for damage.

Repair or replace.

STEP 7. Connector check: C-113 engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector

Q. Is the check result normal?

Go to Step 8 .

Repair or replace.

STEP 8. Check harness between B-20 (terminal No. 3) power steering fluid pressure sensor connector and C-113 (terminal No. 97) engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector.

note

Before checking harness, check intermediate connector B-17, and repair if necessary (R. H. drive vehicles).

Check power supply line for short circuit.

Q. Is the check result normal?

Go to Step 9 .

Repair.

STEP 9. M.U.T.-III data list

Refer to Data List Reference Table

Item B4: Power steering fluid pressure sensor

Q. Is the check result normal?

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points ).

	Replace engine-ECU <M/T> or engine-A/T-ECU <A/T>.

STEP 10. Perform resistance measurement at B-20 power steering fluid pressure sensor

Disconnect connector, and measure at harness side.
Resistance between terminal No. 1 and earth.

OK: 2 Ω or less

Q. Is the check result normal?

Go to Step 13 .

Go to Step 11.

STEP 11. Connector check: C-113 engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector

Q. Is the check result normal?

Go to Step 12 .

Repair or replace.

STEP 12. Check harness between B-20 (terminal No. 1) power steering fluid pressure sensor connector and C-113 (terminal No. 96) engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector.

note

Before checking harness, check intermediate connector B-17 (R. H. drive vehicles) and C-116, and repair if necessary.

Check earthing line for open circuit and damage.

Q. Is the check result normal?

Go to Step 9 .

Repair.

STEP 13. Perform voltage measurement at C-112 engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector.

Measure engine-ECU <M/T> or engine-A/T-ECU <A/T> terminal voltage.
Ignition switch: ON
Voltage between terminal No. 84 and earth.

OK: 1V or less (Steering wheel: Not operated)
Voltage rises (Steering wheel: Operated)

Q. Is the check result normal?

Go to Step 17 .

Go to Step 14 .

STEP 14. Connector check: C-112 engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector

Q. Is the check result normal?

Go to Step 15 .

Repair or replace.

STEP 15. Check harness between B-20 (terminal No. 2) power steering fluid pressure sensor connector and C-112 (terminal No. 84) engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector.

note

Before checking harness, check intermediate connector B-17 (R. H. drive vehicles), and repair if necessary.

Check output line for open/short circuit and damage.

Q. Is the check result normal?

Go to Step 16 .

Repair.

STEP 16. Check harness between B-20 (terminal No. 3) power steering fluid pressure sensor connector and C-113 (terminal No. 97) engine-ECU <M/T> connector or engine-A/T-ECU <A/T> connector.

note

Before checking harness, check intermediate connector B-17, and repair if necessary (R. H. drive vehicles).

Check power supply line for damage.

Q. Is the check result normal?

Replace power steering pressure sensor.

Repair.

STEP 17. Connector check: C-112 engine-ECU <M/T> connectors or engine-A/T-ECU <A/T> connector

Q. Is the check result normal?

Go to Step 9 .

Repair or replace.