DTC 121

DE. DTC 1-2-1
1-2-1 Short-circuit to ground in solenoid S1 circuit

Principle of operation

Solenoid S1 performs gearshifting in combination with solenoid S2. The solenoid operates when supplied with battery voltage from the TCM, which delivers an upshifting or downshifting signal depending on the speed of the car, the throttle position and the selected driving mode.

Fault description

A short-circuit to ground has occurred at some point in the solenoid S1 circuit and the solenoid is not receiving a supply. The emergency limp-home program is activated and the transmission operates only in 4th gear (i.e. solenoid S1 cannot perform gearshifting). The MIL on the panel lights.
Troubleshooting should indicate if the short-circuit is in the lead between the TCM and S1, in S1 or in the TCM.





Circuit description

The circuit consists of the TCM, three connectors and solenoid S1 in the transmission.





1
Testing solenoid S1 in test mode 4

- Move gear selector lever to position P.

Test solenoid S1 in test mode 4 use a stethoscope to hear solenoid click more clearly. Displaying & Reading Trouble Codes

- If solenoid does not click, fault is permanent.
- If solenoid clicks, fault is occurring only intermittently under particular conditions, making it considerably more difficult to locate.




2
Measuring resistance of solenoid and wiring

- Switch off ignition.
- Connect break-out box to wiring.

Measure resistance between # 8 (51) and # 12 (SG) with ohmmeter.

- If instrument indicates 10-15 Ohms, solenoid and leads are OK.
Check leads and connectors for open-circuits and poor connections as described in Testing and Inspection. Component Tests and General Diagnostics

If this check indicates that leads and connections are OK, DTC is due to intermittent fault. Return to Testing and Inspection. Diagnostic Procedures

- If instrument indicates other value, proceed to next step.





3
Measuring solenoid resistance

- Switch off ignition.
- Measure at connector E on transmission (solenoid side).

Connect ohmmeter between terminal 1 and ground terminal on transmission.

- If instrument indicates under 10 Ohm or over 15 Ohm, solenoid S1 or wiring between solenoid and connector on transmission is faulty. proceed to next step.
- If instrument indicates 10-15 Ohms, solenoid S1 and wiring are OK.
In that case, check wiring for short-circuit to ground as described in Testing and Inspection. Component Tests and General Diagnostics

Return to Testing and Inspection. Diagnostic Procedures

TCM may be faulty if DTC is again displayed after test driving although test indicates that resistance is correct.

4
Measuring resistance of control system

- Remove Transmission pan to gain access to Solenoids.
- Disconnect solenoid S1 connector.

Measure resistance between pin on solenoid S1 and ground terminal on transmission.

- Solenoid is faulty if instrument indicates under 10 Ohm or over 15 Ohm. Replace solenoid.
- If instrument indicates 10-15 Ohm, solenoid S1 is OK.
In that case, fault is in wiring harness between transmission connector and solenoid S1. Replace harness.

Return to Testing and Inspection. Diagnostic Procedures