Service Manual2005 Diagnostic Trouble Code (DTC) P1781

Nubira-Lacetti

Diagnostic Trouble Code (DTC) P1781

Engine Torque Signal Error

Conditions for Setting the DTC

TCM detects that malfunction of engine speed signal for 2 seconds.
No DTC U2105

Action Taken When the DTC Sets

TCM will request the illumination of MIL and store DTC when TCM detects a failure on the first ignition cycle.
No engine torque reduction control
No engagement pressure control
No 4th gear
No self-learning control

Conditions for Clearing the DTC

The TCM turns off the MIL when no further failures detected for three consecutive ignition cycles.
The scan tool can clear the DTC from the TCM history.
The TCM clears the DTC from the TCM history memory after forty consecutive warm up cycles without fault.

Cause of Failure

Wiring harness or connector between ECM and TCM
ECM
TCM

DTC P1781 Engine Torque Signal Error

Step	Action	Value(s)	Yes	No
1	Turn the ignition OFF. Install the Scan tool. With the engine OFF, turn the ignition switch to the ON position. Select Store Freeze Frame/Failure Records from the Diagnostic Trouble Codes Information menu. Store Freeze Frame/Failure Records. Select Clear DTC Information from the Diagnostic Trouble Codes Information menu. Clear DTC Information. Perform one vehicle drive cycles. Is the Malfunction Indicator Lamp (MIL) ON?	-	Go to Step 2	Repair the temporary connection failure of connector.
2	Select Request DTC by Status from the Diagnostic Trouble Codes Information menu. Request DTC by Status. Is DTC P1781 displayed?	-	Go to Step 3	Repair the temporary connection failure of connector.
3	Turn the ignition OFF. Disconnect the TCM wiring connector and ECM wiring connector. Measure the resistance between terminal A17 of the TCM wiring connector and terminal 88 of the ECM wiring connector. Measure the resistance between terminal A7 of the TCM wiring connector and terminal 57 of the ECM wiring connector. Is the resistance within the values shown?	0 Ω	Go to Step 5	Go to Step 4
4	Repair the malfunctioning terminals as necessary. Is the action complete?	-	System OK	-
5	Turn the ignition ON. Measure the voltage of terminal A17. Measure the voltage of terminal A7. Is the voltage within the values shown?	11-14 v	Go to Step 6	Go to Step 7
6	Repair the malfunctioning terminals as necessary. Is the action complete?	-	System OK	-
7	Inspect the "Engine Speed". Refer to Section 1F, Diagnosis. Was a problem found?	-	Refer to Section 1F, Diagnosis.	Go to Step 8
8	Replace the TCM. Turn the ignition OFF. Turn the ignition ON. Check if P1781 DTC is set. Is the DTC set?	-	Go to Step 9	Go to Step 10
9	Replace the ECM. Is the action complete?	-	Go to Step 10	-
10	After the repair, use a scan tool "clear info" function and road test the vehicle. Review the "DTC info". Has the last test failed or is the current DTC displayed?	-	Begin diagnosis again	Repair verified exit DTC chart

Diagnostic Trouble Code (DTC) P1791

Throttle Position Signal Error

Conditions for Setting the DTC

TCM detects that malfunction of throttle position signal for 2 seconds continuously.
No DTC U2105

Action Taken When the DTC Sets

TCM will request the illumination of MIL and store DTC when TCM detects a failure on the first ignition cycle.
TCM judges the throttle opening is 0% for shift point control.
TCM judges the throttle opening is 100% for line pressure control.
No lock-up
No 4th gear
No self-learning control
No timing solenoid control for N-D

Conditions for Clearing the DTC

The TCM turns off the MIL when no further failures detected for three consecutive ignition cycles.
The scan tool can clear the DTC from the TCM history.
The TCM clears the DTC from the TCM history memory after forty consecutive warm up cycles without fault.

Cause of Failure

Wiring harness or connector between ECM and TCM
ECM
TCM

DTC 1791 Throttle Position Signal Error

Step	Action	Value(s)	Yes	No
1	Turn the ignition OFF. Install the Scan tool. With the engine OFF, turn the ignition switch to the ON position. Select Store Freeze Frame/Failure Records from the Diagnostic Trouble Codes Information menu. Store Freeze Frame/Failure Records. Select Clear DTC Information from the Diagnostic Trouble Codes Information menu. Clear DTC Information. Perform one vehicle drive cycle. Is the Malfunction Indicator Lamp (MIL) ON?	-	Go to Step 2	Repair the temporary connection failure of connector.
2	Select Request DTC by Status from the Diagnostic Trouble Codes Information menu. Request DTC by Status. Is DTC P1791 displayed?	-	Go to Step 3	Repair the temporary connection failure of connector.
3	Turn the ignition OFF. Disconnect the TCM wiring connector and ECM wiring connector. Measure the resistance between terminal A17 of the TCM wiring connector and terminal 88 of the ECM wiring connector. Measure the resistance between terminal A7 of the TCM wiring connector and terminal 57 of the ECM wiring connector. Is the resistance within the values shown?	0 Ω	Go to Step 5	Go to Step 4
4	Repair the malfunctioning terminals as necessary. Is the action complete?	-	System OK	-
5	Turn the ignition ON. Measure the voltage of terminal A17. Measure the voltage of terminal A7. Is the voltage within the values shown?	11-14 v	Go to Step 6	Go to Step 7
6	Repair the malfunctioning terminals as necessary. Is the action complete?	-	System OK	-
7	Replace the TCM. Turn the ignition OFF. Turn the ignition ON. Check if P1791 DTC is set. Is the DTC set?	-	Go to Step 8	Go to Step 9
8	Replace the ECM. Is the action complete?	-	Go to Step 9	-
9	After the repair, use a scan tool "clear info" function and road test the vehicle. Review the "DTC info". Has the last test failed or is the current DTC displayed?	-	Begin diagnosis again	Repair verified exit DTC chart

Diagnostic Trouble Code (DTC) P1792

Engine Coolant Temperature (ECT) Signal Error

Conditions for Setting the DTC

TCM detects malfunction of Engine Coolant Temperature (ECT) signal for 2 seconds continuously.
No DTC U2105

Action Taken When the DTC Sets

TCM will not request the illumination of MIL, but will store DTC when TCM detects a failure on the first ignition cycle.
TCM judges the engine coolant temperature 90 degrees when lapse 15 minutes from ignition ON.

Conditions for Clearing the DTC

The scan tool can clear the DTC from the TCM history.
The TCM clears the DTC from the TCM history memory after forty consecutive warm up cycles without fault.

Cause of Failure

Wiring harness or connector between ECM and TCM
ECM
TCM

DTC P1792 Engine Coolant Temperature (ECT) Signal Error

Step	Action	Value(s)	Yes	No
1	Turn the ignition OFF. Install the Scan tool. With the engine OFF, turn the ignition switch to the ON position. Select Clear DTC Information from the Diagnostic Trouble Codes Information menu. Clear DTC Information. Perform one vehicle drive cycle. Select Request DTC by Status from the Diagnostic Trouble Codes Information menu. Request DTC by Status. Is DTC P1792 displayed?	-	Go to Step 2	Repair the temporary connection failure of connector.
2	Turn the ignition OFF. Disconnect the TCM wiring connector and ECM wiring connector. Measure the resistance between terminal A17 of the TCM wiring connector and terminal 88 of the ECM wiring connector. Measure the resistance between terminal A7 of the TCM wiring connector and terminal 57 of the ECM wiring connector. Is the resistance within the values shown?	0 Ω	Go to Step 4	Go to Step 3
3	Repair the malfunctioning terminals as necessary. Is the action complete?	-	System OK	-
4	Turn the ignition ON. Measure the voltage of terminal A17. Measure the voltage of terminal A7. Is the voltage within the values shown?	11-14 v	Go to Step 5	Go to Step 6
5	Repair the malfunctioning terminals as necessary. Is the action complete?	-	System OK	-
6	Replace the TCM. Turn the ignition OFF. Turn the ignition ON. Check if P1792 DTC is set. Is the DTC set?	-	Go to Step 7	Go to Step 8
7	Replace the ECM. Is the action complete?	-	Go to Step 8	-
8	After the repair, use a scan tool "clear info" function and road test the vehicle. Review the "DTC info". Has the last test failed or is the current DTC displayed?	-	Begin diagnosis again	Repair verified exit DTC chart

Diagnostic Trouble Code (DTC) U2105

Can Error

Conditions for Setting the DTC

TCM detects that the BUS OFF signal. This detection is continued for 0.2 seconds.
TCM detects that nothing of ECM signal on CAN BUS for 0.2 seconds. This detection is continued for 2.0 seconds.

Action Taken When the DTC Sets

TCM will request the illumination of MIL and store DTC when TCM detects a failure on the first ignition cycle.
TCM judges the throttle opening is 0% for shift point and lock-up point control.
TCM judges the throttle opening is 100% for line pressure control.
No lock-up
No self-learning control
No 4th gear
TCM judges the engine revolution is 0 rpm.

Conditions for Clearing the DTC

The TCM turns off the MIL when no further failures detected for three consecutive ignition cycles.
The scan tool can clear the DTC from the TCM history.
TCM detects the BUS normal signal for 2 seconds continuously.

Cause of Failure

Wiring harness or connector between ECM and TCM
ECM
TCM

DTC U2105 CAN Error

Step	Action	Value(s)	Yes	No
1	Turn the ignition OFF. Install the Scan tool. With the engine OFF, turn the ignition switch to the ON position. Select Store Freeze Frame/Failure Records from the Diagnostic Trouble Codes Information menu. Store Freeze Frame/Failure Records. Select Clear DTC Information from the Diagnostic Trouble Codes Information menu. Clear DTC Information. Perform one vehicle drive cycle. Is the Malfunction Indicator Lamp (MIL) ON?	-	Go to Step 2	Repair the temporary connection failure of connector.
2	Select Request DTC by Status from the Diagnostic Trouble Codes Information menu. Request DTC by Status. Is DTC U2105 displayed?	-	Go to Step 3	Repair the temporary connection failure of connector.
3	Turn the ignition OFF. Disconnect the TCM wiring connector and ECM wiring connector. Measure the resistance between terminal A17 of the TCM wiring connector and terminal 88 of the ECM wiring connector. Measure the resistance between terminal A7 of the TCM wiring connector and terminal 57 of the ECM wiring connector. Is the resistance within the values shown?	0 Ω	Go to Step 5	Go to Step 4
4	Repair the malfunctioning terminals as necessary. Is the action complete?	-	System OK	-
5	Turn the ignition ON. Measure the voltage of terminal A17. Measure the voltage of terminal A7. Is the voltage within the values shown?	11-14 v	Go to Step 6	Go to Step 7
6	Repair the malfunctioning terminals as necessary. Is the action complete?	-	System OK	-
7	Replace the TCM. Turn the ignition OFF. Turn the ignition ON. Check if U2105 DTC is set. Is the DTC set?	-	Go to Step 8	Go to Step 9
8	Replace the ECM. Is the action complete?	-	Go to Step 9	-
9	After the repair, use a scan tool "clear info" function and road test the vehicle. Review the "DTC info". Has the last test failed or is the current DTC displayed?	-	Begin diagnosis again	Repair verified exit DTC chart