Pinpoint Test B: The Courtesy Lamps Do Not Illuminate With The Liftgate Open

Interior Lighting

Pinpoint Test B: The Courtesy Lamps Do Not Illuminate With The Liftgate Open

Normal Operation

The Body Control Module (BCM) sends a voltage signal to the liftgate ajar switch (manual liftgate) or the Liftgate/Trunk Module (LTM) (power liftgate).

For vehicles with a manual liftgate, the voltage signal is then routed to ground through the liftgate ajar switch. The liftgate ajar switch is closed when the liftgate is closed. When the liftgate is opened, the signal to ground is interrupted, indicating an open liftgate to the BCM (Body Control Module).

For vehicles with a power liftgate, the LTM (Liftgate/Trunk Module) provides ground to the BCM (Body Control Module) through the liftgate ajar input circuit when the liftgate is closed. When the liftgate is opened, the LTM (Liftgate/Trunk Module) removes ground, indicating an open liftgate to the BCM (Body Control Module).

When the BCM (Body Control Module) detects the liftgate is open, voltage is provided to the courtesy lamps.

- DTC B2721 (Liftgate/Decklid Ajar Output Short to Ground or Open)- a continuous and on-demand DTC that sets when the LTM (Liftgate/Trunk Module) detects a short to ground from the BCM (Body Control Module) liftgate ajar input circuit.

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors

- Liftgate latch (manual liftgate)

- LTM (Liftgate/Trunk Module) (power liftgate)

- BCM (Body Control Module)

PINPOINT TEST B : THE COURTESY LAMPS DO NOT ILLUMINATE WITH THE LIFTGATE OPEN

NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

B1 CHECK THE COURTESY LAMP OPERATION FROM ANY DOOR

- Ignition OFF.

- Open any door and observe the courtesy lamps.

Do the courtesy lamps illuminate?

Yes
GO to B2.

No
GO to Pinpoint Test A. Pinpoint Test A: The Courtesy Lamps Do Not Illuminate With A Door Open

B2 CHECK THE LTM (Liftgate/Trunk Module) OR THE LIFTGATE LATCH

- Disconnect: Liftgate Latch C479 (Manual Liftgate) or LTM (Liftgate/Trunk Module) C4174B (Power Liftgate).

Do the courtesy lamps illuminate?

Yes
If equipped with a manual liftgate, INSTALL a new liftgate latch. TEST the system for normal operation.

If equipped with a power liftgate, GO to B4.

No
GO to B3.

B3 CHECK THE LIFTGATE AJAR INPUT CIRCUIT FOR A SHORT TO GROUND

- Disconnect: BCM (Body Control Module) C2280C.

- Measure the resistance between the BCM (Body Control Module) C2280C-19, circuit CPL58 (GY/OG), harness side and ground.






Is the resistance greater than 10,000 ohms?

Yes
GO to B5.

No
REPAIR circuit CPL58 (GY/OG) for a short to ground. CLEAR the DTCs. TEST the system for normal operation.

B4 CHECK FOR CORRECT LTM (Liftgate/Trunk Module) OPERATION

- Disconnect all the LTM (Liftgate/Trunk Module) connectors.

- Check for:
- corrosion

- damaged pins

- pushed-out pins


- Connect all the LTM (Liftgate/Trunk Module) connectors and make sure they seat correctly.

- Operate the system and verify the concern is still present.

Is the concern still present?

Yes
INSTALL a new LTM (Liftgate/Trunk Module). TEST the system for normal operation.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs.

B5 CHECK FOR CORRECT BCM (Body Control Module) OPERATION

- Disconnect all the BCM (Body Control Module) connectors.

- Check for:
- corrosion

- damaged pins

- pushed-out pins


- Connect all the BCM (Body Control Module) connectors and make sure they seat correctly.

- Operate the system and verify the concern is still present.

Is the concern still present?

Yes
INSTALL a new BCM (Body Control Module). TEST the system for normal operation.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.