C1258

4WD Switch Circuit Malfunction - Part 1 Of 2:

4WD Switch Circuit Malfunction - Part 2 Of 2:

CIRCUIT DESCRIPTION
Current is supplied to the 4WD indicator lamp through the IG Fuse (hot with ignition switch in ON and START positions.) The 4WD switch is open when the transfer case is set in either 2H or N range.

In 2H mode, the 4WD Signal circuit is supplied with current flowing through the 4WD indicator lamp bulb filament. The EBCM senses this current and determines the vehicle is in 2H mode.

In 4H/4L mode, the 4WD Signal circuit is grounded by the 4WD switch. This causes to turn on the 4WD indicator lamp and signals the EBCM that the vehicle is in 4WD.

CONDITIONS FOR RUNNING THE DTC
^ Vehicle is in 4 wheel drive.
^ Ignition voltage is greater than 9 volts.

CONDITIONS FOR SETTING THE DTC
^ This DTC can be set anytime after initialization is completed.
^ A malfunction exists if the EBCM detects an open in the 4WD Signal circuit.

ACTION TAKEN WHEN THE DTC SETS
^ A malfunction DTC stores.
^ ABS remains functional.

CONDITIONS FOR CLEARING THE DTC
^ The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used.
^ 100 drive cycles pass with no DTCs detected. A drive cycle consists of starting the vehicle, driving the vehicle over 16 km/h (10 mph), stopping and then turning the ignition OFF.

DIAGNOSTIC AIDS
Possible causes:
^ Open in the 4WD Signal circuit or the 4WD indicator circuit
^ Open in the 4WD switch circuit
^ Open 4WD indicator lamp bulb
^ Open IG Fuse
^ Malfunctioning PCM Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction.

Thoroughly inspect any circuitry that may cause the intermittent complaint for the following conditions:
^ A poor connection
^ Rubbed-through wire insulation
^ A broken wire inside the insulation
^ Backed out terminals
^ Improper mating
^ Broken locks
^ Improperly formed or damaged terminals
^ Poor terminal-to-wiring connections
^ Physical damage to the wiring harness

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
4. This step ensures the 4WD switch is in the closed position.
6. This step tests the 4WD switch.
8. This step determines if the fault exists in the EBCM or the PCM.