Powertrain Controls - ECM/PCM

DTC 42 Fuel Temperature Circuit Low (High Temperature Indicated):

Fuel Temperature Circuit Low (High 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) 42 WILL SET WHEN
Fuel temperature greater than 102°C (215°F) for 2 seconds.

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

DTC 42 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 42 is a hard failure or an intermittent condition.
2. This test will determine if CKT 1578 is shorted to ground.

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