P1791
TP SIGNAL SYSTEM RANGE/PERFORMANCE - P1790The throttle signal is a pulse width modulated (pwm) input which runs at a constant frequency of 183 Hz the information is contained in the duty cycle of the signal. If this information is out of range, that is, the duty cycle is less than 5 % or greater than 94 %, then the TCM will use a substitute throttle value of 47 % and will light the warning lamp and this fault code will be stored. During cranking, this signal is used to convey the engine coolant temperature.
The coolant temperature signal persists for 500 msec after reaching the engine run threshold of 400 rpm. If the TCM does not recognize a valid throttle angle signal after this time then a substitute throttle value (47 %) will be used and the warning lamp will be lit and this fault code will be stored. A fault code will only be stored if the engine speed is greater than 400 rpm. If an out of range coolant temperature is received then a substitute coolant temperature value (77 °C) is used but no fault is stored.
TP ELECTRICAL SIGNAL SYSTEM - P1791
If the throttle angle signal line is held permanently high or low for more than 100 ms, then this fault will be recognized and stored. The TCM will adopt the substitute throttle value and turn on the warning lamp. The fault code will only be stored if the engine speed is greater than 400 rpm.
Possible Causes:
Faulty harness wiring 1 connection.
Faulty ECM signal.
Effects:
Transmission warning lamp illuminated.
MIL illuminated.
Normal mode only available.
Substitute throttle angle adopted.
No kickdown facility.
Remedy:
Repair or renew harness / 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