Short-Circuit To Ground Or Open-Circuit

Other Diagnostic Trouble Codes
- Read off OTHER DTCs.
- Is diagnostic trouble code (DTC) AT-123 stored?

Yes:
- Proceed to: Fault-tracing Information section below.

No:
- Proceed to: Checking Solenoid STH section below.

Fault-tracing Information
- Fault-trace according to diagnostic trouble code AT-123. AT-123 System Pressure Solenoid STH
- Proceed to: Verification section below.





Checking Solenoid STH
- Ignition ON.
- Go into scrolling values.
- Read off current in solenoid circuit.
- Depress accelerator pedal (AP) slowly.
- The current should decrease as the accelerator pedal is depressed.

If reading is OK:
- Proceed to: Checking For Open-circuit, Contact Resistance And Oxidation section below.

If reading is incorrect:
- Proceed to: Checking Power Ground section below.





Checking Power Ground
- Ignition OFF.
- Connect the test box and check ground terminals.
- Check the power ground carefully.
- Is the reading OK?

Yes:
- Proceed to: Checking Voltage Drop Over Signal Ground And Power Ground section below.

No:
- Proceed to: Fault-tracing Information section below.

Fault-tracing Information
- The diagnostic trouble code has been caused by a poor power ground.
- Proceed to: Verification section below.





Checking Voltage Drop Over Signal Ground And Power Ground
- Ignition OFF.
- Connect transmission control module.
- Ignition ON.
- Turn on as many power consuming items as possible.
- Connect a voltmeter between # 15 and # 1 on the test box.
- The voltmeter should read less than 0.6 Volts.

If reading is OK:
- Proceed to: Checking Resistance In Solenoid STH Circuit section below.

If reading is incorrect:
- Proceed to: Checking For Open-circuit, Contact Resistance And Oxidation section below.





Checking For Open-circuit, Contact Resistance And Oxidation
- Ignition OFF.
- Check ground terminals 31/53 and 31/66, cables between ground terminal and transmission control module (TCM) and transmission control module connector for an open-circuit, contact resistance and oxidation.
- Proceed to: Verification section below.





Checking Resistance In Solenoid STH Circuit
- Ignition OFF.
- Disconnect engine control module (ECM).
- Connect an ohmmeter between # 4 and # 16 on test box.
- The ohmmeter should read 2 - 6 Ohms.

If reading is OK:
- Proceed to: Checking Solenoid STH Circuit For Short-circuit To Ground section below.

If reading is incorrect:
- Proceed to: Checking Resistance In Solenoid STH Circuit In The Transmission section below.





Checking Resistance In Solenoid STH Circuit In The Transmission
- Ignition OFF.
- Raise the car to access the transmission.
- Carefully clean round connector D.
- Disconnect transmission connector D.
- Connect an ohmmeter between transmission connector D terminals 4 and 5 (transmission side).
- The ohmmeter should read 2 - 6 Ohms.

If reading is OK:
- Proceed to: Checking Resistance In The Control Signal Cable section below.

If reading is incorrect:
- Proceed to: Checking Resistance In Solenoid STH section below.





Checking Resistance In Solenoid STH
- Ignition OFF.
- Open the control system.
- Disconnect solenoid STH.
- Connect ohmmeter between the pins in the solenoid connector.
- The ohmmeter should read 2 - 6 Ohms.

If reading is OK:
- Proceed to: Checking For An Open-circuit section below.

If reading is incorrect:
- Proceed to: Replacing Component section below.





Checking For An Open-circuit
- Check cables between solenoid STH and transmission connector D terminals 4 and 5 for an open-circuit.
- Proceed to: Verification section below.





Replacing Component
- Ignition OFF.
- Replace transmission control system.
- Proceed to: Verification section below.





Checking Resistance In The Control Signal Cable
- Ignition OFF.
- Transmission connector D disconnected.
- Connect an ohmmeter between transmission connector terminal 4 (transmission control module side) and # 16 on the test box.
- The ohmmeter should read approx. 0 Ohms.

If reading is OK:
- Proceed to: Checking Signal Cable Resistance section below.

If reading is incorrect:
- Proceed to: Checking For An Open-circuit section below.





Checking For An Open-circuit
- Check cable between transmission connector D terminal 4 and transmission control module # 16 for an open-circuit.
- Proceed to: Verification section below.





Checking Signal Cable Resistance
- Ignition OFF.
- Transmission connector D disconnected.
- Connect an ohmmeter between transmission connector D terminal 5 (transmission control module side) and # 4 on the test box.
- The ohmmeter should read approx. 0 Ohms.

If reading is OK:
- Proceed to: Checking For Loose Connections, Contact Resistance And Oxidation section below.

If reading is incorrect:
- Proceed to: Checking For An Open-Circuit section below.





Checking For Loose Connections, Contact Resistance And Oxidation
- Ignition OFF.
- The diagnostic trouble code was caused by loose connections in the transmission control module or transmission connectors.
- Check the connectors for loose connections and remedy. Check contact resistance and oxidation.
- Proceed to: Verification section below.





Checking For An Open-Circuit
- Check cable between transmission connector D terminal 5 and transmission control module # 4 for an open-circuit.
- Proceed to: Verification section below.

Checking Solenoid STH Circuit For Short-circuit To Ground
- Ignition OFF.
- Engine control module disconnected.
- Connect an ohmmeter between # 16 on the test box and transmission housing.
- The ohmmeter should read infinite resistance.

If reading is OK:
- Proceed to: Checking The Control Signal Cable For A Short-circuit To Supply Voltage section below.

If reading is incorrect:
- Proceed to: Checking Solenoid STH Circuit In The Transmission For A Short-circuit To Ground section below.





Checking Solenoid STH Circuit In The Transmission For A Short-circuit To Ground
- Ignition OFF.
- Raise the car to access the transmission.
- Transmission connector D disconnected.
- Connect an ohmmeter between transmission connector D terminal 4 (transmission side) and transmission housing.
- The ohmmeter should read infinite resistance.

If reading is OK:
- Proceed to: Checking Signal Cable Resistance To Ground section below.

If reading is incorrect:
- Proceed to: Checking Solenoid STH For Resistance To Ground section below.





Checking Solenoid STH For Resistance To Ground
- Ignition OFF.
- Open the control system.
- Disconnect solenoid STH.
- Connect an ohmmeter between one of the pins in the solenoid connector and the transmission housing.
- The ohmmeter should read infinite resistance.

If reading is OK:
- Proceed to: Checking For A Short-circuit section below.

If reading is incorrect:
- Proceed to: Replacing Component section below.





Checking For A Short-circuit
- Check cables between solenoid STH and transmission connector D terminals 4 and 5 for a short-circuit to ground.
- Proceed to: Verification section below.





Replacing Component
- Ignition OFF.
- Replace transmission control system.
- Proceed to: Verification section below.





Checking Signal Cable Resistance To Ground
- Ignition OFF.
- Engine control module disconnected.
- Transmission connector D disconnected.
- Connect an ohmmeter between # 16 on the test box and transmission housing.
- The ohmmeter should read infinite resistance.

If reading is OK:
- Proceed to: Checking For A Short-circuit section below.

If reading is incorrect:
- Proceed to: Checking For A Short-circuit 2 sections below.





Checking For A Short-circuit
- Check cable between transmission connector D terminal 5 and transmission control module # 4 for a short-circuit to ground.
- Proceed to: Verification section below.





Checking For A Short-circuit
- Check cable between transmission connector D terminal 4 and transmission control module # 16 for a short-circuit to ground.
- Proceed to: Verification section below.





Checking The Control Signal Cable For A Short-circuit To Supply Voltage
- Ignition OFF.
- Test box connected.
- Connect transmission control module.
- Ignition on.
- Connect a voltmeter between # 16 and # 1 on the test box.
- The voltmeter should read 0 - 6 Volts.

If reading is OK:
- Proceed to: Checking Signal Cable For Short-circuit To Supply Voltage section below.

If reading is incorrect:
- Proceed to: Checking For A Short-circuit section below.





Checking For A Short-circuit
- Check cable between solenoid STH and transmission control module # 16 for a short-circuit to supply voltage.
- Proceed to: Checking The Transmission Control Module section below.





Checking Signal Cable For Short-circuit To Supply Voltage
- Ignition ON.
- Connect a voltmeter between # 4 and # 1 on the test box.
- The voltmeter should read 0 - 2 Volts.

If reading is OK:
- Proceed to: Checking Signal Cable For Short-circuit To Supply Voltage section below.

If reading is incorrect:
- Proceed to: Checking For A Short-circuit section below.





Checking Signal Cable For Short-circuit To Supply Voltage
- The transmission control module can malfunction if there has been a short-circuit to supply voltage in the solenoid STH circuit. Check the transmission control module as follows:

- Ignition OFF.
- Reconnect connectors, reinstall components etc.
- Ignition ON.
- Go into scrolling values.
- Read off current in solenoid circuit.
- Depress accelerator pedal slowly.

- The current should decrease as the accelerator pedal is depressed.

If reading is OK:
- Proceed to: Checking For Contact Resistance And Oxidation section below.

If reading is incorrect:
- Proceed to: Replacing Component section below.





Checking For Contact Resistance And Oxidation
- Ignition OFF.
- The diagnostic trouble code was caused by poor contact in the transmission control module or transmission connectors. Check connector for contact resistance and oxidation and remedy.
- Proceed to: Verification section below.





Checking For A Short-circuit
- Check cable between solenoid STH and transmission control module # 4 for a short-circuit to supply voltage.
- Proceed to: Checking The Transmission Control Module section below.





Checking The Transmission Control Module
- The transmission control module can malfunction if there has been a short-circuit to supply voltage in the solenoid STH circuit. Check the transmission control module as follows:

- Ignition OFF.
- Reconnect connectors, reinstall components etc.
- Ignition ON.
- Go into scrolling values.
- Read off current in solenoid circuit.
- Depress accelerator pedal slowly.

- The current should decrease as the accelerator pedal is depressed.

If reading is OK:
- Proceed to: Fault-tracing Information section below.

If reading is incorrect:
- Proceed to: Replacing Component section below.

Fault-tracing Information
- Transmission control module is OK.
- Fault corrected.





Replacing Component
- Ignition OFF.
- Try a new transmission control module.

NOTE: It is important that the solenoid STH circuit is not short-circuited to battery voltage. A short-circuit can damage the new transmission control module.

- Proceed to: Verification section below.





Verification
- After repairs have been completed they must be verified as follows to ensure that the fault has been eliminated:

- Ignition OFF.
- Reconnect connectors, reinstall components etc.
- Ignition ON.
- Select scrolling values.
- Read off current in solenoid circuit.
- Depress accelerator pedal slowly.

- The current should decrease as the accelerator pedal is depressed.

If reading is OK:
- Fault corrected.

If reading is incorrect:
- Proceed to: Fault-tracing Information section below.

Fault-tracing Information
The verification result shows that the fault persists.

- Do you want to exit fault-tracing?

Yes:
- Fault not corrected.

No:
- Proceed to: Other Diagnostic Trouble Codes section above.





Intermittent Fault
- Ignition OFF.
- Check transmission and transmission control module connectors for loose connections, contact resistance and oxidation.
- Check cable between solenoid STH and transmission control module # 16 and # 4 for an intermittent open-circuit, and intermittent short-circuit to ground.
- Check cable between ground terminal 31/66 and transmission control module # 1 for an intermittent open-circuit.
- Check ground terminal 31/66 for contact resistance and oxidation.
- Proceed to: Verification section below.

Fault-tracing Information
For intermittent faults fault-tracing is not followed by a verification because the fault is not present at this moment.

- Do you want to repeat fault-tracing?

Yes:
- Proceed to: Other Diagnostic Trouble Codes section above.

No:
- Operation done.