For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptor

DTC B153A 08: Liftgate Latch Switch Signal Circuit Signal Performance -- Signal Invalid

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Liftgate Position Sensor 5 V Reference Voltage | B153E 08 | 2 | 2 | --
Liftgate Disable Signal | 1, 2 | 1 | 1 | --
Liftgate Open Signal -- Exterior Switch | B396E 02 | 1 | 1 | --
Liftgate Open Signal -- Shut Face Switch | B396E 02 | 1 | 1 | --
Object Sensors Signal | B153F 02 | B153F 05 | B153F 05 | B153F 03, B153F 07
Liftgate Open Signal -- Exterior Switch | B396E 02 | 1 | 1 | --
Open/Close Switches Signal | B396D 02 | 1, 2 | 1, 2 | --
Pawl Switch Signal | B153A 08 | B153A 08 | B153A 08 | B153A 08
Position Sensor Signal 1 | B153E 08 | B153E 08 | B153E 08 | B153E 08
Position Sensor Signal 2 | B153E 08 | B153E 08 | B153E 08 | B153E 08
Ratchet Switch Signal | B153A 08 | B153A 08 | B153A 08 | B153A 08
Sector Switch Signal | B153A 08 | B153A 08 | B153A 08 | B153A 08
Liftgate Latch Cinch Control | B2495 02 | B2495 04 | B2495 01 | --
Liftgate Latch Release Control | B2495 02 | B2495 04 | B2495 01 | --
Liftgate Motor Close Control | B396A 02 | B396A 04 | B396A 01 | --
Liftgate Motor Open Control | B396A 02 | B396A 04 | B396A 01 | --
Liftgate Switches Low Reference | -- | B153A 08 | 1 | B153E 08
Position Sensor Low Reference | -- | B0153E 08 | 2 | --
Mode/Release Switch Ground | -- | 1 | 1 | --
Liftgate Control Module Ground | -- | U0230 00 | 2 | --
1. Liftgate Switch Malfunction 2. Liftgate Malfunction

### Circuit/System Description

The ratchet, pawl, and sector switches are part of the liftgate latch assembly and are used by the liftgate control module to determine the state of the latch during the process of latching or unlatching. The ratchet and pawl switches will be inactive when the primary and secondary latches are latched, and the sector switch will be active during the power cinch function. Each of the latch switch signal circuits are supplied battery voltage through a resistor and monitored within the liftgate control module. The latch switches share a common low reference circuit from the liftgate control module and when the switch contacts close the signal circuit goes low and the liftgate control module determines the switch to be active. The full open switch is a limit switch mounted on the gear motor assembly alongside the swing arm gear. The full open switch signal circuit is supplied battery voltage through a resistor and monitored within the liftgate control module. When the liftgate reaches the full open position, the switch signal circuit is closed to the low reference circuit and the signal circuit voltage goes low.

### Conditions for Running the DTC

The system voltage is 9.5-16 V.

### Conditions for Setting the DTC

Any incorrect combination of signals from the following switch inputs:

• | Ratchet switch

• | Pawl switch

• | Sector switch

### Action Taken When the DTC Sets

• | Power open will be disabled.

• | The latch may be inoperative or not function normally.

### Conditions for Clearing the DTC

• | The DTC will be current for as long as the fault is present.

• | When the fault is no longer present, the DTC will be a history DTC.

• | A history DTC will clear after 50 ignition cycles.

### Diagnostic Aids

Note: Before testing can be performed the liftgate must be opened. Refer to Opening the Liftgate Without Electrical Power for the appropriate procedure.

• | Whenever the liftgate control module loses power or is disconnected, the ignition must be cycled OFF then ON in order to reactivate the liftgate control module.

• | DTC B153A may be set when the vehicle is driven while the liftgate is open, as when the owner transports a large package in the rear of the vehicle. The DTC will become history after the liftgate is closed and does not affect normal liftgate operation.

### Reference Information

#### Schematic Reference

Liftgate Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Rear Hatch/Gate Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, observe the scan tool Liftgate Latch Pawl Switch parameter while opening and closing the liftgate. The parameter should change between Active and Inactive.
2. Observe the scan tool Liftgate Latch Ratchet Switch parameter while opening and closing the liftgate. The parameter should change between Active and Inactive.
3. Observe the scan tool Liftgate Latch Sector Switch parameter while opening and closing the liftgate. The parameter should change between Active and Inactive.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the M31 Liftgate Latch Assembly.
2. Ignition OFF, test for less than 1.0 Ω between the low reference circuit terminal 2 and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K39 Liftgate Control Module.

3. Ignition ON, verify the scan tool Liftgate Latch Pawl Switch parameter is Inactive.

⇒ | If not the specified value, test the signal circuit terminal 5 for a short to ground. If the circuit tests normal, replace the K39 Liftgate Control Module.

4. Verify the scan tool Liftgate Latch Ratchet Switch parameter is Inactive.

⇒ | If not the specified value, test the signal circuit terminal 6 for a short to ground. If the circuit tests normal, replace the K39 Liftgate Control Module.

5. Verify the scan tool Liftgate Latch Sector Switch parameter is Inactive.

⇒ | If not the specified value, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the K39 Liftgate Control Module.

6. Install a 3 A fused jumper wire between the signal circuit terminal 5 and low reference circuit terminal 2. Verify the scan tool Liftgate Latch Pawl Switch parameter is Active.

⇒ | If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K39 Liftgate Control Module.

7. Install a 3 A fused jumper wire between the signal circuit terminal 6 and low reference circuit terminal 2. Verify the scan tool Liftgate Latch Ratchet Switch parameter is Active.

⇒ | If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K39 Liftgate Control Module.

8. Install a 3 A fused jumper wire between the signal circuit terminal 4 and low reference circuit terminal 2. Verify the scan tool Liftgate Latch Sector Switch parameter is Active.

⇒ | If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K39 Liftgate Control Module.

9. If all circuits test normal, test or replace the M31 Liftgate Latch Assembly.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Liftgate Latch Replacement

• | Control Module References for liftgate control module replacement, setup and programming