Control Module System - Revised Diagnostic Aids
File In Section: 6E - Engine Fuel & EmissionBulletin No.: 51-65-66
Date: October, 1995
SERVICE MANUAL UPDATE
Subject:
Section 3B - Control Module System (VCM-A) - Revised Diagnostic Aids
Models:
1995 Chevrolet and GMC Truck S/T Models
with Automatic and Manual Transmission and 4.3L Engine (VIN W - RPO L35)
This bulletin is being issued to reverse the Diagnostic Aids for:
^ DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit-Low Input
^ DTC P1114 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent Low Input
^ DTC P0118 Engine Coolant Temperature (ECT) Sensor Circuit-High Input
^ DTC P1115 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Input
These diagnostics are contained in the 1995-S/T Driveability, Emissions and Electrical Diagnosis Manual # GMT/95-ST. Pages 3B-58, 3B-60 and 3B-142, 3B-144 should read as follows:
P0117, P1114
Check harness routing for a potential short to ground in the 5 volt reference circuit.
The scan tool displays engine temperature in degrees centigrade. After engine is started, the temperature should rise steadily to about 90°C, then stabilize when thermostat opens.
The "Temperature vs. Resistance Value" scale may be used to test the coolant sensor at various temperature levels to evaluate the possibility of a "skewed" (mis-scaled) sensor. A "skewed" sensor could result in poor driveability concerns.
P0118, P1115
A faulty connection or an open in the 5 volt reference circuit or the sensor ground circuit will result in a DTC P0118.
The scan tool displays engine temperature in degrees centigrade. After engine is started, the temperature should rise steadily to about 90°C, then stabilize when thermostat opens.
The "Temperature vs. Resistance Value" scale may be used to test the coolant sensor at various temperature levels to evaluate the possibility of a "skewed" (mis-scaled) sensor. A "skewed" sensor could result in poor driveability concerns.