For 1990-2009 cars
ABS Components
Brake Fluid Level Switch, Brake indicator, and Stoplamp Switch

### 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.

1. This step ensures the 4WD switch is in the closed position.

2. This step tests the 4WD switch.

3. This step determines if the fault exists in the EBCM or the PCM.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the ABS Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - ABS
2 | Move the 4WD selector lever in and out of 4WD while observing the 4WD indicator. Is the 4WD indicator ON continuously? | -- | Go to Four-Wheel Drive Indicator Does Not Turn Off in Transfer Case | Go to Step 3
3 | Is the 4WD indicator inoperative? | -- | Go to Four-Wheel Drive Indicator Does Not Light in Transfer Case | Go to Step 4
4 |

1. Install a scan tool.
2. Set the 4WD selector lever to the 4WD position.
3. Turn ON the ignition, with the engine OFF.
4. With a scan tool, observe the 4WD Switch parameter in the 4WD data list.

Does the scan tool display Normal?

--

Go to Step 5

Go to Step 6

5 |

1. Activate the 4WD selector lever.
2. With the scan tool, observe the 4WD Switch parameter.

Does the 4WD Switch parameter change state?

--

Go to Diagnostic Aids

Go to Step 6

6 |

1. Turn OFF the ignition.
2. Disconnect the 4WD switch.
3. Turn ON the ignition, with the engine OFF.
4. With a scan tool, observe the 4WD Switch parameter.

Does the scan tool display Open?

--

Go to Step 11

Go to Step 7

7 |

1. Test the 4WD switch circuit of the PCM for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
2. Test the 4WD switch circuit between the EBCM and the PCM for an open or short to ground.

Connect the J 39700 with the J 39700-99 to the EBCM harness connector only.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 8

8 |

1. Reconnect the PCM and the 4WD switch connectors.
2. Connect the J 39700 with the J 39700-99 to the EBCM harness connector and the EBCM.
3. Turn the ignition switch to the ON position.
4. Measure the voltage of the 4WD indicator circuit to the EBCM.

Is the voltage measured within the range specified in the Value(s) column?

0-5.5V

Go to Step 9

Go to Step 10

9 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12
10 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13
11 | Inspect for poor connections at the harness connector of the 4WD switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14
12 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the replacement? | -- | Go to Step 15 | --
13 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | Go to Step 15 | --
14 | Replace the 4WD switch. Refer to 4WD Switch Replacement . Did you complete the replacement? | -- | Go to Step 15 | --
15 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK