Pinpoint Test I: The Rear Window Defrost System Is Inoperative

WARNING: This page is about a different car, the 2021 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

Refer to HEATED WINDOW for schematic and connector information.

Normal Operation and Fault Conditions

REFER to: Glass, Frames and Mechanisms - System Operation and Component Description .

DTC Fault Trigger Conditions

DTC	Description	Fault Trigger Condition
BCMC B15E5:11	Rear Heated Windscreen Output: Circuit Short To Ground	If equipped with diesel engine, sets when the BCMC detects a short to ground on the rear window defrost output circuit.
BCMC B15E5:15	Rear Heated Windscreen Output: Circuit Short To Battery Or Open	If equipped with diesel engine, sets when the BCMC detects a short to voltage or open in the rear window defrost output circuit.

Possible Sources

Fuse
Wiring, terminals or connectors
Rear window defrost grid
Rear window glass
HVAC module
BCMC

Visual Inspection and Pre-checks

If equipped with gas engine, verify BCMC fuse 50 (40A) is OK.
Inspect the rear window defrost grid and electrical connectors for damage.

I1 CHECK FOR BCMC (BODY CONTROL MODULE C) DIAGNOSTIC TROUBLE CODES (DTCS)
- Ignition OFF.
- Ignition ON.
- Using a diagnostic scan tool, perform BCMC self-test.
Is BCMCDTC U0164:87 present?

Yes REFER to: Body Control Module C (BCMC) .

No GO to I2

I2 CHECK THE REAR WINDOW DEFROST GRID TERMINALS FOR DAMAGE
- Inspect the rear window defrost grid terminals and electrical connectors for damage.
Are the rear window defrost grid terminals OK?

Yes GO to I3

No REPAIR the rear window defrost grid terminal as necessary. REFER to: Lead Terminal Repair .

I3 CHECK THE REAR WINDOW DEFROST GRID VOLTAGE

Ignition OFF.

Disconnect: Heated Rear Window Element C402A.

Start the engine.

Activate the rear window defrost switch.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C402A-1	Courtesy of FORD MOTOR COMPANY	Ground

Is the voltage greater than 11 volts?

Yes

GO to I4

GO to I5

I4 CHECK THE REAR WINDOW DEFROST GRID GROUND

Ignition OFF.

Disconnect: Heated Rear Window Element C402B.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C402B-1	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance less than 3 ohms?

Yes

REPAIR the rear window defrost grid, INSTALL a new rear window glass sliding panel or INSTALL a new rear window glass assembly if necessary. To repair the defrost grid, REFER to: Heated Window Grid Wire Repair . To install a new rear window glass sliding panel, REFER to: Rear Window Glass Sliding Panel . To install a new rear window glass assembly, REFER to: Fixed Glass .

No	REPAIR the circuit.

I5 CHECK THE REAR WINDOW DEFROST SWITCH PID (PARAMETER IDENTIFICATION)

Start the engine.

Access the HVAC and monitor the CC_SW_R_DEFPID

Monitor the rear window defrost switch PID while pressing and releasing the rear window defrost switch.

Does the PID agree with the rear window defrost switch status?

Yes	If equipped with gas engine, VERIFY BCMC fuse 50 (40A) is OK. If OK, GO to I6. If not OK, REFER to the OEM WIRING DIAGRAMS to identify the possible causes of the circuit short. If equipped with diesel engine, GO to I6

GO to I7

I6 CHECK THE REAR WINDOW DEFROST OUTPUT CIRCUIT FOR AN OPEN OR SHORT TO GROUND

Ignition OFF.

Disconnect: BCMC C1035B (gas engine) or C1035E (diesel engine).

If equipped with gas engine, measure:

Positive Lead	Measurement / Action	Negative Lead
C1035B-31	Courtesy of FORD MOTOR COMPANY	C402A-1
C1035B-31	Courtesy of FORD MOTOR COMPANY	Ground

If equipped with diesel engine, measure:

Positive Lead	Measurement / Action	Negative Lead
C1035E-5	Courtesy of FORD MOTOR COMPANY	C402A-1
C1035E-5	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance less than 3 ohms between the BCMC and the rear window defrost grid connector, and greater than 10, 000 ohms between the BCMC and ground?

Yes

GO to I8

No	REPAIR the circuit.

I7 CHECK FOR CORRECT HVAC (HEATING, VENTILATION AND AIR CONDITIONING) MODULE OPERATION

Ignition OFF.

Disconnect and inspect all the HVAC module connectors.

Repair:
- corrosion (install new connector or terminals - clean module pins)
- damaged or bent pins - install new terminals/pins as necessary
- pushed-out pins - install new pins as necessary

Reconnect the HVAC module connectors and all previously disconnected rear window defrost system connectors. Make sure they seat and latch correctly.

Operate the system and determine if the concern is still present.

Is the concern still present?

Yes

CHECK OASIS for any applicable service articles: TSB, GSB, SSM or FSA. If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, INSTALL a new HVAC module. REFER to: Heating, Ventilation and Air Conditioning (HVAC) Control Module .

No	The system is operating correctly at this time. The concern may have been caused by poor connections. ADDRESS the root cause of any connector or pin issues.

I8 CHECK FOR CORRECT BCMC (BODY CONTROL MODULE C) OPERATION

Ignition OFF.

Disconnect and inspect all the BCMC connectors.

Repair:
- corrosion (install new connector or terminals - clean module pins)
- damaged or bent pins - install new terminals/pins as necessary
- pushed-out pins - install new pins as necessary

Reconnect the BCMC connectors and all previously disconnected rear window defrost system connectors. Make sure they seat and latch correctly.

Operate the system and determine if the concern is still present.

Is the concern still present?

Yes	CHECK OASIS for any applicable service articles: TSB, GSB, SSM or FSA. If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, INSTALL a new BCMC. REFER to: Body Control Module C (BCMC) .

No	The system is operating correctly at this time. The concern may have been caused by poor connections. ADDRESS the root cause of any connector or pin issues.