DTC 245

EL. DTC 2-4-5
2-4-5 Open-circuit or short-circuit to ground in torque reduction circuit

Principle of operation

Under certain gearshifting conditions, the engine torque is reduced to make the operation smoother and to reduce transmission wear. The TCM supplies the Motronic 1.8 ECM with signals (TC1/TC2) for this purpose and receives an acknowledgement signal in return. The signals retard the ignition timing to reduce the engine torque.

Fault description

On receipt of the signal from the TCM, the Motronic ECM transmits an acknowledgement to the TCM that the torque reduction request has been received. DTC 2-4-5 will be recorded if this signal is not received by the TCM and the MIL will light.





Circuit description

The circuit consists of the TCM, the Motronic 1.8 ECM and the associated wiring and connectors.





1
Measuring torque reduction signal voltage at Motronic 1:8 ECM

- Switch off ignition.
- Remove fuse 24.
- Connect break-out box to Motronic 1.8 ECM.
- Install fuse 24.
- Switch on ignition.
- Start engine.

Test torque reduction signals TC1 and TC2 in test mode 4 while measuring as described below. Test Mode 4: Entry of Commands






Connect voltmeter to break-out box.

(Rapid oscillations in the reading (approx. 1 second) may be difficult to read, especially when using a digital voltmeter.)

Measure voltage across # 50 and # 19 (SG). Activate TC1.

- Reading should oscillate between 0 and 5 V. Measure voltage across # 51 and # 19 (SG). Activate TC2.
- Reading should oscillate between 0 and 5 V.

Activate TC1 and TC2 in turn in test mode 4 and measure voltage (acknowledgement signal to TCM) between # 43 and # 19 in each case.

- Reading should oscillate between 0 and 5 V in both instances.

Conclusions

If readings are correct, TCM is transmitting torque reduction signals TC1 and TC2 to Motronic 1.8 ECM and the ECM is returning an acknowledgement signal to the TCM. Proceed to step 2.

If TC1 and TC2 signals are correct but no acknowledgement has been transmitted, fault is in Motronic 1.8 ECM. Carry out troubleshooting as described in Computers and Control Systems, Testing and Inspection. Testing and Inspection

If TC1 and/or TC2 signals are incorrect, fault is in leads or in TCM. Proceed to step 2.





2
Measuring torque reduction signal voltage at AW 30-4O/AW 30-43 ECM

- Switch off ignition.
- Remove fuse 24.
- Connect break-out box to TCM.
- Install fuse 24.
- Switch on ignition.

Test torque reduction signals TC1 and TC2 in test mode 4 while measuring as described below. Displaying & Reading Trouble Codes






Connect voltmeter to break-out box.

(Rapid oscillations in the reading (approx. 1 second) may be difficult to read, especially when using a digital voltmeter.)

Measure voltage across # 37 (TC1) and # 12 (SG). ActivateTC1.

- Reading should oscillate between 0 and 5 V.

Measure voltage across # 36 (TC2) and # 12 (SG). Activate TC2.

- Reading should oscillate between 0 and 5 V.

Measure voltage across # 35 (TCM) and # 12 (SG). Activate both TC1 and TC2 (TCM = acknowledgement signal).

- Reading should oscillate between 0 and 5 V.

Conclusions

If TC1 and/or TC2 signals are incorrect, fault is in TCM.
If TCM signal is incorrect in step 2 but correct in step 1, fault is in lead to TCM.
If all readings are correct but fault persists, fault is in TCM.

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