P1780
TORQUE REDUCTION SIGNAL - P1780The diagnostic for this signal is based entirely on feedback from the ECM. If the torque reduction request is active for greater than 2 seconds, the ECM starts the torque reduction fault time-out (10 seconds). If the signal returns to the standby condition within this time, the time-out is reset. If the time-out matures then the ECM stores a fault code and transmits 93 % on the torque signal line and also lights the MIL where necessary.
The ECM will also initiate the torque reduction fault time-out if the signal line is permanently high or low for greater than 125 ms. The conditions for resetting the time-out and the actions if the time-out matures are the same as previously described above. When the TCM receives the correct indication on the torque signal line, this fault code will be stored and a substitute function will be adopted and the warning lamp will be illuminated. The engine management will send normal torque signal when the torque reduction signal returns to standby or when the ignition is reset.
This torque reduction signal is used during gearshifts to convey the actual amount of retard to be applied to the ignition advance angle after the other trims. The signal idles at 17 % (or 12 % if the TCM wishes to drive the MIL ON), and changes to 20 % at the start of a gearshift. This represents 0, retard. When an amount of retard is required, the PWM will increase to the desired value (between 20 % and 90 %) and return to 20 % and then to idle state at the end of the shift.
Pin Outs
TORQUE SIGNAL MALFUNCTION - P1781
The torque signal is a PWM signal from the ECM to the TCM which conveys information about the actual torque developed by the engine in the range 0 to 510 Nm. The base frequency is 91 Hz and the signal which is active low should be within the range 10 % to 90 % modulation.
The torque signal is monitored continuously during initialization and operation. If the frequency of the signal is incorrect or the signal is out of range, then this fault code will be flagged. The TCM will adopt a substitute function and the warning lamp will be illuminated. This fault code will only be flagged if the engine speed is above 448 rpm.
Possible Causes:
Faulty harness wiring 1 connector.
Faulty signal from ECM.
Effects:
Transmission warning lamp illuminated.
Substitute torque signal adopted by TOM.
Normal mode only available.
No kickdown facility.
Maximum fluid pressure applied.
Remedy:
Repair or renew harness 1 connector.
Examine ECM fault diagnosis.
Troubleshooting Schematic
Key To Schematic Diagrams
1. Transmission Control Module (TCM)
2. Transmission Unit
3. TCM Multi-pin Connector
4. Transmission Rotary Switch
5. Transmission Connector Plug
6. Engine Control Module
7. Instrument Pack
8. ABS/Traction Control Control Module
9. Kickdown Switch
Pin Outs