Possible Causes

WARNING: This page is about a different car, the 2020 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

Wiring, terminals or connectors
ATCM

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

Fig 1: All Terrain Control Module (ATCM) Connector - C3639

Courtesy of FORD MOTOR CO.

Harness Side

Circuit

Fig 2: Body Control Module-A (BCM-A) Connector - C2280A

Courtesy of FORD MOTOR CO.

Harness Side

Circuit

OA1: CHECK FOR ABS MODULE DTCS

Put the ABS module in sleep mode by performing the following steps:
- With ALL doors closed, set the ignition from ON to OFF.
- Disconnect the diagnostic scan tool.
- Open the door, exit the vehicle and close the door.
- Wait a minimum of 90 seconds for the ABS module to enter sleep mode.
Ignition ON, engine OFF.
Carry out the ABS self-test.
Retrieve and record all ABS module DTCs.

Are there any "lost communication" or "invalid data" DTCs other than U0401:86 present in the ABS module?

Yes	No
DIAGNOSE all other ABS module "lost communication" and "invalid data" DTCs before continuing with this pinpoint test. REFER to the ABS module DTC Chart.	Go to OA2.

OA2: VERIFY THE ATCM COMMUNICATES ON THE NETWORK

Ignition ON, engine OFF.
Using a diagnostic scan tool, carry out the Network Test.

Does the ATCM pass the Network Test?

Yes	No
Go to OA3.	DIAGNOSE the ATCM does not respond to the scan tool. REFER to the Module Communications Network article.

OA3: CHECK FOR ATCM DTCS

Carry out the ATCM self-test.

Are any DTCs present?

Yes	No
REFER to the appropriate Four-Wheel Drive Systems article.	Go to OA4.

OA4: CHECK FOR ABS MODULE DTCS

Review the recorded DTCs from Step OA1.

Is any U0138:xx or U0439:xx DTC present in the ABS module?

Yes	No
GO to PINPOINT TEST BM .	Go to OA5.

OA5: VERIFY ALL WIRING CONNECTIONS

Ignition OFF.
ATCM connector disconnected. (C3639)
BCM_A connector disconnected. (C2280A)
Using a good light source, inspect all disconnected electrical connectors for the following:
- corrosion - install new connector or terminal and clean the module pins
- damaged or bent pins - install new terminals or pins
- pushed-out pins - install new pins as necessary
- spread terminals - install new terminals as necessary

Are the connectors free of corrosion, damaged pins, bent pins, pushed-out pins and spread terminals?

Yes	No
Go to OA6.	REPAIR the affected connectors or terminals. REFER to Connector Repair Procedures article schematic and connector information.

OA6: CHECK FOR CORRECT ATCM OPERATION

ATCM connector connected. (C3639) Make sure the connector seats and latches correctly.
BCM_A connector connected. (C2280A) Make sure the connector seats and latches correctly.
Operate the system and determine if the concern is still present.

Is the concern is still present?

Yes	No
INSTALL a new ATCM. CHECK OASIS for any 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 ATCM. REFER to the appropriate Four-Wheel Drive Systems article.	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.

OA7: CHECK FOR IPC DTCS

Carry out the IPC self-test.

Are there any DTCs in the IPC?

Yes	No
DIAGNOSE all IPC DTCs before diagnosing ABS module DTCs C1000:86 or U0401:86. REFER to the Instrumentation, Message Center and Warning Chimes article.	Go to OA8.

OA8: CHECK THE HILL DESCENT CONTROL SWITCH

Ignition OFF.
Press and hold the Hill Descent Control switch while taking the measurement.