0318909 JOHNSON COVER

Recommended Repairs
Extended Heating Cycle (Any Cycle)
Replace the control module for the air inlet heater (if equipped).Note: Cycle times are approximate only. Some variance does not necessarily indicate a system failure.No Heating Cycles
Hot engine components can cause injury from burns. Before performing maintenance on the engine, allow the engine and the components to cool.
Check for the following problems:
Faulty control module
Faulty oil pressure switch
Faulty coolant temperature sensor
Faulty heater element
Faulty power relay (magnetic switch)System Check
Note: The step-by-step procedures that follow are diagnostic checks that must be performed in sequence. Failure to follow the sequence may result in an incorrect diagnosis and unnecessary expense.
Lamp test
Preheat cycle
Crank heat cycle
Regular heat cycle
Heater element
Coolant temperature sensor
Oil pressure switchLamp Test
Inspect the lamp. Replace the lamp, if necessary.
Check the wiring harness for the lamp for damaged wires and for poor connections.
If the lamp does not illuminate after the lamp and the harness has been inspected, proceed with the tests that follow.Note: If the coolant temperature is below 18.3° 2.7°C (65° 5°F), the system should go directly from the lamp test into the preheat cycle. The lamp will not turn off.Preheat Cycle
Remove the cover from the controller in order to gain access to the power relay. With the help of an assistant, turn the ignition switch to the RUN position and feel the power relay (magnetic switch) for a click. The click indicates that the relay energized. If the power relay does not click, proceed with the following steps.Note: Perform the following steps while the preheat cycle is active. The preheat cycle is active for thirty seconds. It may be necessary to reactivate the preheat cycle periodically while these diagnostic checks are performed. To reactivate the preheat cycle, turn the ignition switch to OFF and then turn the ignition switch back to RUN. The results will be incorrect if any of the steps are performed and the preheat cycle is inactive.
Disconnect the electrical connector at the control module. Attach a voltmeter between terminal "F" and terminal "A" of the vehicle side of the wiring harness.
With the ignition switch in the RUN position, the voltmeter should read 12 volts.
If the voltmeter does not read a voltage, inspect the vehicle wiring for a blown fuse, a damaged wire, or a poor connection. Check both the power wire (terminal "F") and the ground wire (terminal "A").
If the voltmeter reads 12 volts, reconnect the connector.
Disconnect the connector for the coolant temperature sensor from the wiring harness. Use a small jumper wire to connect the two terminals of the connector on the vehicle side of the wiring harness.
With the help of an assistant, turn the ignition switch to the RUN position and feel the power relay (magnetic switch) for a click that indicates that the relay energized.
If a click is felt, one of the following conditions exists:
The coolant temperature is above 29.4 °C (85 °F).
The coolant temperature sensor has not reset to the closed position because the coolant temperature is not below 18.3 °C (65 °F).
The coolant temperature sensor is faulty.Perform the "Coolant Temperature Sensor" test. Replace the coolant temperature sensor, if necessary.
If a click is not felt and the leads to the coolant temperature sensor are jumpered, connect a test light to the power relay. Power should be present at both terminals on the coil side of the relay.
If power is present on the relay terminal that connects to the control module but not on the relay terminal that connects to the heater, replace the relay.
If power is present on both sides of the relay, remove the ground lead from the relay. The ground wire attaches to terminal "D" of the control module. Ground the relay to the cylinder block. If the relay energizes, the control module is faulty. Replace the control module.
If the power relay (magnetic switch) energizes, but the heater does not operate, use a test light to check for power on the contact side of the relay. Lack of power indicates a wiring problem. Check the vehicle's harness for a damaged wire or a poor connection.
If power is present on the relay terminal that connects to the heater and the heater does not operate, inspect the ground wire to the heater. If there are no defects, perform the "Heater Element" test.Crank Heat Cycle
If the air inlet heater does not work during the crank cycle, proceed with the following steps.
Follow Step 1 through Step 10 of