Pinpoint Test B: P0645:00

WARNING: This page is about a different car, the 2023 Ford Bronco. However, it is still accessible from the selected car via links, so may be relevant.

Refer to MANUAL CLIMATE CONTROL SYSTEM for schematic and connector information.

Normal Operation and Fault Conditions

Voltage is provided to the A/C clutch SMART Field-Effect Transistor (FET) at all times. The A/C clutch SMART (FET) is a non serviceable part of the printed circuit board on the BCMC [also known as BJB ].

When A/C is requested and no fault conditions are present, the PCM grounds the A/C clutch control input circuit that is hardwired to the A/C clutch SMART (FET) processing in the BCMC. For additional information on A/C Request, REFER to: Climate Control System - Vehicles With: Electronic Manual Temperature Control (EMTC) - System Operation and Component Description .

DTC Fault Trigger Conditions

DTC	Description	Fault Trigger Condition
PCM P0645:00	A/C Clutch Relay Control Circuit: No Sub Type Information	Sets when the PCM grounds the SMART (FET) control input circuit and more current than expected is detected on the circuit. The DTC also sets when the control input circuit is off and voltage is detected on the circuit.

Possible Sources

Wiring, terminals or connectors
A/C clutch control FET (non-serviceable, part of the BCMC)
PCM

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

B1 CHECK THE A/C (AIR CONDITIONING) CLUTCH SMART FET (FIELD-EFFECT TRANSISTOR) INPUT CONTROL CIRCUIT FOR A SHORT TO VOLTAGE

Ignition OFF.

Disconnect PCM C175B (2.3L) or C1551B (2.7L).

Ignition ON.

Measure:

2.3L Input Circuit from Powertrain Control Module (PCM) to Body Control Module C (BCMC)

Positive Lead	Measurement / Action	Negative Lead
C175B Pin 67	Courtesy of FORD MOTOR COMPANY	Ground

2.7L Input Circuit from Powertrain Control Module (PCM) to Body Control Module C (BCMC)

Positive Lead	Measurement / Action	Negative Lead
C1551B Pin 44	Courtesy of FORD MOTOR COMPANY	Ground

Is any voltage present?

Yes	REPAIR the circuit.

GO to B2

B2 CHECK THE A/C (AIR CONDITIONING) CLUTCH SMART FET (FIELD-EFFECT TRANSISTOR) INPUT CONTROL CIRCUIT FOR A SHORT TO GROUND

Ignition OFF.

Measure:

2.3L Input Circuit from Powertrain Control Module (PCM) to Body Control Module C (BCMC)

Positive Lead	Measurement / Action	Negative Lead
C175B Pin 67	Courtesy of FORD MOTOR COMPANY	Ground

2.7L Input Circuit from Powertrain Control Module (PCM) to Body Control Module C (BCMC)

Positive Lead	Measurement / Action	Negative Lead
C1551B Pin 44	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance greater than 10, 000 ohms?

Yes

GO to B3

No	REPAIR the circuit.

B3 CHECK THE A/C (AIR CONDITIONING) CLUTCH SMART FET (FIELD-EFFECT TRANSISTOR) INPUT CONTROL CIRCUIT FOR AN OPEN

Disconnect BJB

Measure:

2.3L Input Circuit from Powertrain Control Module (PCM) to Body Control Module C (BCMC)

Positive Lead	Measurement / Action	Negative Lead
C175B Pin 67	Courtesy of FORD MOTOR COMPANY	C1035A Pin 20

2.7L Input Circuit from Powertrain Control Module (PCM) to Body Control Module C (BCMC)

Positive Lead	Measurement / Action	Negative Lead
C1551B Pin 44	Courtesy of FORD MOTOR COMPANY	C1035A Pin 20

Is the resistance less than 3 ohms?

Yes	CLEAR codes and CARRY OUT the PCM self-test. If the concern is still present, GO to B4

No	REPAIR the circuit.

B4 CHECK FOR CORRECT PCM (POWERTRAIN CONTROL MODULE) OPERATION

Ignition OFF.

Disconnect and inspect all PCM electrical connectors (if not previously disconnected).

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

Connect all PCM electrical 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 PCM. Refer to POWERTRAIN CONTROL MODULE (PCM) - 2.3L EcoBoost (199kW 270PS) , or refer to POWERTRAIN CONTROL MODULE (PCM) - 2.7L EcoBoost (238kW 324PS) , or refer to POWERTRAIN CONTROL MODULE (PCM) - 3.0L EcoBoost (299kW 406PS) (DD) .

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