DTC 22

Diagnostic Chart:

Electrical Schematic:

CIRCUIT DESCRIPTION
The Engine Coolant Temperature (ECT) sensor is a thermistor (a variable resistor that changes along with ECT changes) in series with a fixed resistor within the PCM. The PCM applies 5 volts to the sensor. The PCM monitors the voltage across the ECT sensor and converts it into a temperature reading. When the engine is cold the ECT sensor resistance is high, and when the engine is warm the ECT sensor resistance is low. Therefore, when the engine is cold the PCM will receive a high voltage input, and when the engine is warm the PCM will receive a low voltage input.

DTC 22 will set if either of the following conditions are met for at least 0.5 seconds:
^ Voltage input at the PCM indicates a very low ECT.
^ Voltage input at the PCM indicates a very high ECT.

DTC CHART TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.
1. This checks for an open or short to ground in the WHT wire between the PCM and ECT sensor and for a faulty PCM.
2. This checks for an open in the BRN wire between the PCM and the ECT sensor and for a faulty PCM.
3. This determines if the problem is a faulty ECT sensor or PCM.

DIAGNOSTIC AIDS
Verify that the engine is not overheating and has not been subjected to conditions which could create an overheating condition (i.e.., overload, trailer towing, hilly terrain, heavy stop and go traffic, etc.).

A "shifted" (mis-scaled) sensor could result in poor driveability complaints. Measure the resistance of the ECT sensor according to the diagnostic aids chart on the diagnostic chart. If DTCs 24, 31 and 41 are also set, the malfunction may be in the sensor ground circuit.

INTERMITTENT MALFUNCTIONS
An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect hamess connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connections before component replacement.