DTC 131

DJ. DTC 1-3-1
1-3-1 Open-circuit or short-circuit to ground in solenoid STH circuit

Principle of operation

Solenoid STH controls the transmission fluid pressure. The solenoid is operated by a variable current from the TCM, the value of which is influenced primarily by the throttle. The pressure is low at high current levels (approx. 1 A). The line pressure is a maximum at low currents or when the current is interrupted.

Fault description

Open-circuit or short-circuit to ground in solenoid STH circuit. In the case of an open-circuit or short-circuit, the line pressure will be too high, resulting in 'hard' gearshifting and loss of the lock-up function. The MIL will light.

Troubleshooting should indicate if STH lead, STH ground lead or solenoid is open or short circuited, or if TCM is faulty.





Circuit description

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





1
Testing solenoid STH in test mode 4

- Move gear selector lever to position P.

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

Note!
Since solenoid clicks only twice (on and off operation), listen carefully with stethoscope for sound.

- 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.

Connect ohmmeter between # 3 (STH) and # 4 (STHG).

- If instrument indicates value between 2 and 6 Ohm, circuit is not open-circuited.
- If instrument indicates value greater than 6 Ohm, circuit is open-circuited.

Measure resistance between # 3 (STH) and ground terminal on transmission, and between # 4 (STHG) and ground terminal on transmission.

- Instrument should indicate infinite resistance.
- If instrument indicates approx. 0 Ohm, circuit is shorted.





3
Measurement of solenoid resistance

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

Connect ohmmeter between terminals 4 (STH) and 5 (STHG).

- If instrument indicates value between 2 and 6 Ohm, circuit is not open-circuited.
- If instrument indicates value greater than 6 Ohm, circuit is open-circuited.

Measure resistance between # 4 (STH) and ground terminal on transmission, and between # 5 (STHG) and ground terminal on transmission.

- Instrument should indicate infinite resistance.
- If instrument indicates approx. 0 Ohm, circuit between connector and solenoid STH is shorted.

Conclusions, step 3

If results of step 2 are wrong but those of step 3 are correct, fault is in wiring harness between TCM and transmission.

If results of step 3 are wrong, fault is in transmission wiring harness between connector and solenoid or in solenoid STH. Proceed to next step.





4
Measuring resistance of control system

- Remove Transmission pan to gain access to Solenoids.

Connect ohmmeter between solenoid terminals.
Instrument should indicate between 2 and 6 Ohm.
Connect ohmmeter between each solenoid terminal and ground terminal on transmission.

- Instrument should indicate infinite resistance.

Conclusions, step 4

If results of step 3 are wrong but those of step 4 are correct, fault is in solenoid wiring harness. Replace harness.
If results of step 4 are wrong, solenoid is faulty. Replace Solenoid.




5
Checking TCM supply

- Switch off ignition.
- Connect break-out box between TCM and wiring.
- Switch on ignition.

Supply between Ignition switch and power ground

Connect voltmeter across # 14 (+12 V) and # 11 (PG).

- Instrument should indicate battery voltage.

Supply between battery and signal ground

Connect voltmeter across # 30 (+12 V) and # 12 (SG).

- Instrument should indicate battery voltage.

Proceed to following step.

6
Checking signal ground and power ground

- Switch on ignition.

Connect voltmeter across # 11 (PG) and # 12 (SG).

- Instrument should indicate less than 0.7 volt, otherwise ground connections are poor. In this case, check leads and connections to ground terminals as described in Testing and Inspection. Component Tests and General Diagnostics

If readings are correct, return to Testing and Inspection. Diagnostic Procedures

If DTC recurs following test drive, try with new TCM.