SERVICE MANUAL NUMBER 23
TROUBLE CODE DIAGNOSTICS - 454/502 MAG MPI & 8.2L MPI
90-861326--1 MARCH 1999 Page 5F-5
Code 14 (2 of 3): Engine Coolant Temperature (ECT) Sensor Circuit
(Non-Scan)
TEST DESCRIPTION:
Number(s) below refer to step number(s) on the diagnostic table.
Step 2. This step checks if there is a problem with the ECM and wiring or if the problem is
the coolant sensor.
Step 3. This step will isolate the problem to CKT 410 (5 volt reference) or to the sensor
ground.
Step 6. Check the harness terminals thoroughly for loose connection. If the resistance or
the coolant sensor is monitored, the resistance should steadily decrease as the engine cool-
ant warms up. The resistance reading would stabilize when the thermostat opens.
Step 7. This step identifies if CKT 410 is open or shorted to ground.
IMPORTANT: If replacing the ECT, tighten hand tight plus 2-1/2 turns maximum.
STEP ACTION VALUE YES NO
PROCEED TO
1
Was the “On-Board Diagnostic” (OBD) System
Check Performed?
– Step 2
Go to
OBD
System
Check
2 1. Ignition OFF.
2. Disconnect ECT sensor connector.
3. Ignition ON, engine OFF.
4. Connect DVOM across coolant sensor
harness terminals.
Is voltage above 4 volts?
Step 6 Step 3
3
1. Connect positive DVOM lead from har-
ness terminal “B” CKT 410 (5 volt reference).
2. Connect negative DVOM lead to a good
ground (–) on engine.
Is voltage above 4 volts?
Step 10 Step 4
4 1. Remove DVOM.
2. Ignition ON.
3. Connect a test light to battery positive
(B+).
4. Touch test light to sensor harness termi-
nal “B” (CKT 410).
Is test light on?
Step 7 Step 5
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