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 fusible link (23). |
| 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 <4A/T, 5A/T-LHD>or C-34 <5A/T-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. |
|