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 engine-A/T-ECU
DIAGNOSIS PROCEDURE |
STEP 1. M.U.T.-III data list |
Item 8: 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. |
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STEP 2. Check the A/T control relay |
| Refer to . |
Q.
Is the check result normal?
|
| Go to Step 3. |
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| Replace the A/T control relay. |
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STEP 3. Connector check: D-110 A/T control relay connector |
| Check for the contact with terminals. |
Q.
Is the check result normal?
|
| Go to Step 4. |
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| Repair the defective connector. |
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STEP 4. Measure the voltage at A/T control relay connector D-110. |
| 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 8. |
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| Go to Step 5. |
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STEP 5. Connector check: A-03 <LHD> or D-137 <RHD> intermediate connector |
| Check for the contact with terminals. |
Q.
Is the check result normal?
|
| Go to Step 6. |
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| Repair the defective connector. |
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STEP 6. Check the harness between A/T control relay connector D-110 terminal No.1 and battery. |
| Check the power supply line for short and open circuit. |
Q.
Is the check result normal?
|
| Go to Step 7. |
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| Repair the wiring harness. |
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STEP 7. M.U.T.-III data list |
| Item 8: 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 engine-A/T-ECU. |
|
STEP 8. Measure the voltage at the A/T control relay connector D-110. |
| (1)Turn the ignition switch to the ON position. |
| (2)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 11. |
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| Go to Step 9. |
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STEP 9. Connectors check: A-03 <LHD>or D-137 <RHD> intermediate connector, D-401 J/B connector |
| Check for the contact with terminals. |
Q.
Is the check result normal?
|
| Go to Step 10. |
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| Repair the defective connector. |
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STEP 10. Check the wiring harness between A/T control relay connector D-110 terminal No.4 and J/B connector D-401 terminal No.12. |
| Check the power supply line for short and open circuit. |
Q.
Is the check result normal?
|
| Go to Step 7. |
|
| Repair the wiring harness. |
|
STEP 11. Measure the voltage at engine-A/T-ECU connector D-218. |
| (1)Install the A/T control relay. |
| (2)Turn the ignition switch to the ON position. |
| (3)Measure the voltage between engine-A/T-ECU connector D-218 terminal No.123, No.124 and earth. OK: System voltage |
Q.
Is the check result normal?
|
| Go to Step 14. |
|
| Go to Step 12. |
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STEP 12. Connector check: D-218 engine-A/T-ECU connector |
| Check for the contact with terminals. |
Q.
Is the check result normal?
|
| Go to Step 13. |
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| Repair the defective connector. |
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STEP 13. Check the harness between A/T control relay connector D-110 terminal No.3 and engine-A/T-ECU connector D-218 terminal No.123, 124. |
| Check the power supply line for short and open circuit. |
Q.
Is the check result normal?
|
| Go to Step 7. |
|
| Repair the wiring harness. |
|
STEP 14. Connector check: engine-A/T-ECU connector |
| Check for the contact with terminals. |
Q.
Is the check result normal?
|
| Go to Step 15. |
|
| Repair the defective connector. |
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STEP 15. Check the harness between A/T control relay connector D-110 terminal No.2 and engine-A/T-ECU connector D-218 terminal No.127. |
| Check the output line for short and open circuit. |
Q.
Is the check result normal?
|
| Go to Step 7. |
|
| Repair the wiring harness. |
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