Refer to Engine Controls Schematics
Engine Cooling Fans
.
Circuit Description
Ignition voltage is supplied directly to fan control (FC) relay 2 and FC relay 3. The powertrain control module (PCM) controls the relays by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component ON, the voltage of the control circuit should be near 0 volts. When the PCM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be near battery voltage. If the fault detection circuit senses a voltage other than what is expected, this diagnostic trouble code (DTC) will set.
The PCM will monitor the control circuit for the following:
| • | A short to ground |
| • | A short to voltage |
| • | An open circuit |
When the PCM detects any of the above malfunctions, this DTC will set and the affected driver will be disabled.
An open coil winding in only one of the relays or an open in the control circuit between the splice and one of the relays will not be detected by this DTC. If this is suspected, refer to Electric Cooling Fan Diagnosis .
Conditions for Running the DTC
| • | The ignition voltage is between 9-18 volts. |
| • | The engine speed is more than 80 RPM. |
| • | The PCM driver transitions from ON to OFF or from OFF to ON. |
Conditions for Setting the DTC
| • | A short to ground, an open circuit, or a short to battery voltage is detected on the control circuit. |
| • | The condition is present for at least 30 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns the MIL OFF after 3 consecutive drive trips during which the diagnostic runs and passes. |
| • | A last test failed, or the current DTC, clears when the diagnostic runs and passes. |
| • | A History DTC clears after 40 consecutive warm-up cycles, if no other emission related diagnostic failures are reported. |
| • | Use a scan tool in order to clear the MIL diagnostic trouble code. |
| • | Interrupting the PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Powertrain Control Module Description , Clearing Diagnostic Trouble Codes. |
Diagnostic Aids
Notice: Use the connector test adapter kit J 35616-A for any test that
requires probing the following items:
• The PCM harness connectors • The electrical center fuse/relay cavities • The component terminals • The component harness connector
If the problem is intermittent, refer to Intermittent Conditions .
Relay Terminal Identification
Use the following relay cavity tables in order to locate the correct cavities to probe during diagnosis. The table layout corresponds to the cavity layout in the underhood accessory wiring junction block. Four blade relays can be inserted two ways. Use the table and NOT the numbering on the relay to avoid probing incorrectly.
Important: Relay #2 is different (5 blade) from Relays #1 and #3 (4 blade). If Relay #2 is incorrectly replaced by a 4 blade style relay, the system will not function properly.
Top of Junction Block | |
|---|---|
Cooling Fan Relay #2 | |
Switch Power (From Fan 1) | Coil Ground (PCM) |
-- | Switch Load (Fan 2) |
Coil Power (Fuse) | Switch Ground |
Top of Junction Block | |
|---|---|
Cooling Fan Relay #3 | |
Switch Power (Fuse) | Coil Power (Fuse) |
Coil Ground (PCM) | Switch Load (Fan 2) |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Listen for an audible click when the relays operate. Repeat the commands as necessary. Even if only one relay operates, the control circuit is verified operational. An open coil winding in only one of the relays, or an open in the control circuit between the splice and one of the relays will not be detected by this DTC.
-
This check can detect a partially shorted coil which would cause excessive current flow. Leaving the circuit energized for 2 minutes allows the coil to warm up. When warm, the coil may open (Amps drop to 0), or short (goes above 0.75 Amp).
-
If the fuse supplying this circuit is open, the circuitry up to the fan motor, including the fan motor and fan relays, needs to be checked for a short in the wiring or a shorted component.
-
If no trouble is found in the control circuit or the connection at the PCM, the PCM may be damaged, however, this is an extremely unlikely failure.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System check? | -- | ||||||
Do fan relays 2 and 3 turn ON and OFF with each command? | -- | |||||||
3 |
The DMM should display infinite resistance (OL). Does the DMM display infinite resistance? | -- | ||||||
Does the current draw stay within the range shown for both relays? | 0.1-0.75 A | Go to Diagnostic Aids | ||||||
5 |
Does the test lamp turn ON and OFF with each command? | -- | ||||||
6 | Probe the ignition feed circuit to either relay coil in the relay harness connector with the test lamp connected to ground. Does the test lamp illuminate? | -- | ||||||
7 |
Do the relays operate? | -- | ||||||
8 | Check for the following conditions:
Is the action complete? | -- | -- | |||||
9 | Repair the relay control circuit. Is the action complete? | -- | -- | |||||
Repair the ignition feed circuit to the relay coil. Is the action complete? | -- | --
| ||||||
11 | Replace the affected relay. Is the action complete? | -- | -- | |||||
12 | Check for poor connections and terminal tension at the PCM harness connector. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Was a problem found and corrected? | -- | ||||||
|
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||||||
14 |
Does the scan tool indicate that this test ran and passed? | -- | ||||||
15 | Review Captured Info using the scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to the applicable DTC table | System OK |
