Code No.P1788 (P1751) A/T control relay system

OPERATION



DIAGNOSIS CODE SET CONDITION




PROBABLE CAUSES



  • Malfunction of A/T control relay
  • Damaged harness wires and connectors
  • Malfunction of the A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III data list
Item 08: Relay voltage (Refer to data list reference table .)

Q. Is the check result normal?
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction .)
Go to Step 2.

STEP 2. Check the A/T control relay connector
Refer to .

Q. Is the check result normal?
Go to Step 3.
Replace the A/T control relay.

STEP 3. Connector check: A-19X A/T control relay connector

Check for the contact with terminals.

Q. Is the check result normal?

Go to Step 4.

Repair the defective connector.

STEP 4. Measure the voltage at A/T control relay connector A-19X.

Disconnect the A/T control relay, and measure the voltage between terminal No.4 and earth at the relay box side.
OK: System voltage

Q. Is the check result normal?

Go to Step 8.

Go to Step 5.

STEP 5. Connector check: A-115 intermediate connector

Check for the contact with terminals.

Q. Is the check result normal?

Go to Step 6.

Repair the defective connector.

STEP 6. Check the harness between A/T control relay connector A-19X terminal No.4 and battery.

Check the power supply line for short or open circuit.

Q. Is the check result normal?

Go to Step 7.

Repair the wiring harness.

STEP 7. M.U.T.-III data list
Item 08: Relay voltage (Refer to data list reference table .)

Q. Is the check result normal?
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
Replace the A/T-ECU.

STEP 8. Measure the voltage at the A/T control relay connector A-19X.
(1)Turn the ignition switch to the ON position.

(2)Disconnect the A/T control relay, and measure the voltage between terminal No.1 and earth at the relay box side.
OK: System voltage

Q. Is the check result normal?

Go to Step 11.

Go to Step 9.

STEP 9. Connectors check: C-52 <LHD>or C-34 <RHD> intermediate connector, C-208 J/B connector




Check for the contact with terminals.

Q. Is the check result normal?

Go to Step 10.

Repair the defective connector.

STEP 10. Check the wiring harness between A/T control relay connector A-19X terminal No.1 and J/B connector C-208 terminal No.2.



Check the power supply line for short or open circuit.

Q. Is the check result normal?

Go to Step 7.

Repair the wiring harness.

STEP 11. Measure the voltage at A/T-ECU connector C-19.
(1)Install the A/T control relay.
(2)Turn the ignition switch to the ON position.

(3)Measure the voltage between A/T-ECU connector C-19 terminal No.2, No.3 and earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 14.

Go to Step 12.

STEP 12. Connector check: C-19 A/T-ECU connector

Check for the contact with terminals.

Q. Is the check result normal?

Go to Step 13.

Repair the defective connector.

STEP 13. Check the harness between A/T control relay connector A-19X terminal No.3 and A/T-ECU connector C-19 terminal No.2, 3.


Check the power supply line for short or open circuit.

Q. Is the check result normal?

Go to Step 7.

Repair the wiring harness.

STEP 14. Connector check: C-20 A/T-ECU connector

Check for the contact with terminals.

Q. Is the check result normal?

Go to Step 15.

Repair the defective connector.

STEP 15. Check the harness between A/T control relay connector A-19X terminal No.2 and A/T-ECU connector C-20 terminal No.71.


Check the output line for short or open circuit.

Q. Is the check result normal?

Go to Step 7.

Repair the wiring harness.