DTC 5-1-4

5-1-4 ENGINE COOLING FAN HALF SPEED, SIGNAL

Preconditions for DTC
^ If the engine cooling fan's signal lead is short circuited to ground/voltage or if there is a break in the circuit, the ECM interprets this as a fault and DTC 5-1-4 is set.

Substitute value
^ Idle air trim is inhibited.
^ Fuel trim is inhibited.
^ Conditions for fuel shut-off changed.
^ If engine coolant temperature exceeds 1O2°C (216°F) the engine cooling fan starts operating at full speed.

Fault sources
^ Signal too high:
- Signal lead short circuited to voltage supply.
- Defective Fan Control (FC) relay.

^ Signal too low:
- Signal lead, half speed short circuited to ground.
- Signal lead, full speed short circuited to ground.
- Break in signal lead.
- Break in voltage lead to engine cooling fan.
- Contact resistance in connectors.
- Defective FC relay.

Fault symptoms
^ May result in poorer performance.

TESTING PROCEDURE





Status Message
^ Check current status message.

If Status message is: Permanent fault, signal too high:
- Proceed to: PERMANENT FAULT, SIGNAL TOO HIGH section below.
If Status message is: Permanent fault, signal too low:
- Proceed to: PERMANENT FAULT, SIGNAL TOO LOW section below.
If Status message is: Intermittent fault, signal too high:
- Proceed to: INTERMITTENT FAULT, SIGNAL TOO HIGH section below.
If Status message is: Intermittent fault, signal too low:
- Proceed to: INTERMITTENT FAULT, SIGNAL TOO LOW section below.

PERMANENT FAULT, SIGNAL TOO HIGH





Checking the Signal Lead
^ Switch Ignition OFF.
^ Disconnect connector B from the FC relay.
^ Switch Ignition ON.
^ Connect a voltmeter between FC relay connector B, connector 1 (to ECM) and ground.

The voltmeter should show approx. 0 Volts.

If reading is OK:
- Test with a new FC relay.
If reading is incorrect:
- Check the lead between the FC relay connector B1 and ECM A7 for signs of short circuiting to voltage supply.

PERMANENT FAULT, SIGNAL TOO LOW





Checking the Voltage Lead
^ Switch Ignition OFF.
^ Disconnect connector A from the FC relay.
^ Connect a voltmeter between FC relay connector A (to ECM) and ground.

The voltmeter should show battery voltage.

If reading is OK:
- Check the signal lead, half speed.
If reading is incorrect:
- The lead between the starter motor and FC relay has a built-in fusible link. If there is a break in this lead, the probable cause is a short circuit to ground in this circuit.
- Check the relay and fan motor before the lead is replaced.
- Check the lead between the starter motor and FC relay connector A1 for signs of a break.





Checking the Signal Lead, Half Speed
^ Switch Ignition OFF.
^ Connector A disconnected.
^ Disconnect connector B from the FC relay.
^ Connect an ohmmeter between FC relay connector B, connector 1 (to ECM) and ground.

The ohmmeter should show 28 - 38K ohms.

If reading is OK:
- Check the signal lead, full speed.
If the ohmmeter shows approx. 0 ohms:
- Check the lead between the FC relay connector B1 and ECM A7 for signs of short circuiting to ground.
If the ohmmeter shows infinite resistance:
- Check the ECM connectors.





Checking the ECM Connector
^ Switch Ignition OFF.
^ Connectors A and B disconnected.
^ Rectify the ECM connector with regard to contact resistance and oxidation.
^ ECM connected.





^ Connect an ohmmeter between FC relay connector B, connector 1 (to ECM) and ground.

The ohmmeter should show 28 - 38K ohms.

If reading is OK:
- Check the FC relay.
If reading is incorrect:
- Check the lead between the FC relay connector B1 and ECM A7 for signs of a break.





Checking the Signal Lead, Full Speed
^ Switch Ignition OFF.
^ Connectors A and B disconnected.
^ Connect an ohmmeter between FC relay connector B, connector 2 (to ECM) and ground.

The ohmmeter should show 100K ohms - infinite resistance.

If reading is OK:
- Check the FC relay.
If reading is incorrect:
- Check the lead between FC relay connector B2 and ECM A22 for signs of short circuiting to ground.





Checking the Fan Control Relay
^ Switch Ignition OFF.
^ Connect connectors A and B to the FC relay.
^ START the engine and let it run at idling speed.





^ Read off the DTC status message.

If the fault is still permanent:
- Test with a new FC relay.
If the fault is intermittent:
- The source of the DTC is poor contact in the FC relay and/or ECM connector.
- Rectify the connectors with regard to contact resistance and oxidation.

INTERMITTENT FAULT, SIGNAL TOO HIGH





Checking the Leads and Connectors
^ Check the lead between the FC relay connector B1 and ECM A7 for signs of intermittent short circuiting to voltage supply.

INTERMITTENT FAULT, SIGNAL TOO LOW

Checking the Leads and Connectors
^ Check the FC relay's and ECM's connectors for signs of loose connection, contact resistance and oxidation.
^ Check the lead between the FC relay connector B1 and ECM A7 for signs of an intermittent break as well as intermittent short circuiting to ground.
^ Check the lead between the FC relay connector A1 and the starter motor for signs of an intermittent break.