P1812

CIRCUIT DESCRIPTION

The Automatic Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor. When the transmission fluid is cold, the sensor resistance is high. As the transmission fluid warms, the sensor resistance decreases. The TFT range is -40 to +14O°C (-40 to +284°F).

When the PCM detects a high transmission temperature for an extended period of time on the TFT Sensor circuit, then DTC P1812 sets. DTC P1812 is a type D DTC.


CONDITION FOR SETTING THE DTC

^ No TFT DTCs P0712 or P0713.

^ The transmission fluid temperature is hotter than 130°C (266°F) for more than 7 minutes.

ACTION TAKEN WHEN THE DTC SETS

The PCM does not illuminate the Malfunction Indicator Lamp (MIL).


CONDITIONS FOR CLEARING THE DTC

A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.

DIAGNOSTIC AIDS

^ Inspect the wiring for poor electrical connections at the PCM. Inspect the wiring at the transmission 7-way connector. Look for the following conditions:

- A bent terminal

- A backed out terminal

- A damaged terminal

- Poor terminal tension

- A chafed wire

- A broken wire inside the insulation

^ When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

^ Inspect the transmission cooling system for blockage and restrictions.


TEST DESCRIPTION

The number below refers to the step numbers on the diagnostic table.

4. This Step inspects all of the components which could cause a P1812 to set.