Powertrain Controls - ECM/PCM

DTC 43 Fuel Temperature Circuit High (Low Temperature Indicated):

Fuel Temperature Circuit High (Low Temperature Indicated):

CIRCUIT DESCRIPTION
The fuel temperature sensor is a thermistor that controls signal voltage to the Powertrain Control Module (PCM). When the fuel is cold, the sensor resistance is high, therefore the PCM will see high signal voltage. As fuel warms, sensor resistance becomes less and voltage drops. The fuel temperature sensor is integrated with the optical sensor.

DIAGNOSTIC TROUBLE CODE (DTC) 43 WILL SET WHEN
^ Fuel temperature less than -14°C (6°F).
^ Engine running for at least 2 minutes.

ACTION TAKEN (PCM will default to)
Poor idle quality during hot conditions.

DTC 43 WILL CLEAR WHEN
The fault condition(s) no longer exist.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step determines if DTC 43 is a hard failure or an intermittent condition.
2. This test simulates a DTC 42. If the PCM recognizes the low signal voltage (high temp), the PCM and wiring are OK.
3. This test will determine if CKT 1578 is open. There should be 5 volts at sensor connector if measured with J 392OO-DVM. This will determine if there is a wiring problem or a faulty PCM.

DIAGNOSTIC AIDS
A scan tool reads fuel temperature in degrees centigrade. After engine is started, the temperature should rise steadily.
A faulty connection, or an open in CKTs 1578 or 987 will result in a DTC 43.
The "Temperature To Resistance Value" scale at the right may be used to test the fuel sensor at various temperature levels to evaluate the possibility of a "skewed" (mis-scaled) sensor.