Pinpoint Test J: U0100: 87

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 Wiring Diagrams MODULE COMMUNICATIONS NETWORK for schematic and connector information.

Normal Operation and Fault Conditions

In addition to communicating over HS-CAN, the GSM and PCM communicate over a private Powertrain CAN. If the GSM does not receive expected messages from the PCM, it will set a DTC.

DTC Fault Trigger Conditions

DTC	Description	Fault Trigger Condition
GSM U0100: 87	Lost Communication With ECM/PCM "A": Missing Message	This DTC indicates the GSM did not receive some or all of an expected message from the PCM over the Powertrain CAN.

Possible Sources

Low system voltage
Circuit open or shorted
Incorrect PMI
Connectors damaged or pushed-out terminals, corrosion, loose wires and missing or damaged seals
PCM fault

J1 CHECK ALL MODULES FOR LOW VOLTAGE DIAGNOSTIC TROUBLE CODES (DTCS)
- Using a diagnostic scan tool, review all continuous memory diagnostic trouble codes (CMDTCs) in all modules.
Is a low voltage DTC set in any module?

Yes RESOLVE the vehicle voltage concern. REFER to: Charging System - 2.7L EcoBoost (238kW/324PS)/3.5L EcoBoost (BM) .

No GO to J2

J2 CHECK THE PCM (POWERTRAIN CONTROL MODULE) FOR DIAGNOSTIC TROUBLE CODES (DTCS)

Using a diagnostic scan tool, carry out the KOEO and KOERPCM self-tests.

Are any diagnostic trouble codes (DTCs) present in the PCM?

Yes	RESOLVE those diagnostic trouble codes (DTCs) first. REFER to the Master DTC Chart.

No	If the PCM does not respond to the diagnostic scan tool, REFER to: CONTROLLER AREA NETWORK (CAN) MODULE COMMUNICATIONS NETWORK . Otherwise, GO to J3

J3 CHECK THE GSM (GEAR SHIFT MODULE) FOR DIAGNOSTIC TROUBLE CODES (DTCS)

NOTE: If a GSM self-test is carried out, the driver door must be fully closed. A false P166B DTC may set if the driver door is not fully closed during the self-test.
- Using a diagnostic scan tool, carry out the GSM self-test.
Are any system voltage or internal module diagnostic trouble codes (DTCs) present in the GSM?

Yes RESOLVE those diagnostic trouble codes (DTCs) first. REFER to the Diagnostic Trouble Code (DTC) Chart .

No GO to J4

J4 CHECK FOR OTHER CAUSES OF COMMUNICATION CONCERNS

NOTE: If new modules were installed prior to the DTC being set, the module configuration can be incorrectly set during the PMI or the PMI may not have been carried out.

CHECK the vehicle service history for recent service actions related to the PCM or to the GSM. If recent service history is found:
- verify correct replacement module was installed
  - HVBOM may be used to verify correct part application
- verify the configuration of replacement module was correct
  - re-configure module using as-built data if prior configuration is suspect
- verify the module was not obtained from a like vehicle and installed into customer vehicle
  - return the swapped module to source vehicle and obtain new replacement module

Were any causes of a communication concern found in the vehicle service history?

Yes	Follow the above directions to address improper module replacement or configuration. If the correct module was installed and the PMI was completed correctly, GO to J5

GO to J5

J5 ATTEMPT TO DUPLICATE THE DTC (DIAGNOSTIC TROUBLE CODE)

NOTE: If a GSM self-test is carried out, the driver door must be fully closed. A false P166B DTC may set if the driver door is not fully closed during the self-test.

Using a diagnostic scan tool, clear all diagnostic trouble codes (DTCs) from the GSM.

Road test the vehicle.

Using a diagnostic scan tool, carry out the GSM self-test.

Did DTC U0100: 87 return?

Yes

GO to J6

No	The system is operating correctly at this time. The concern may have been caused by a high network traffic event or an intermittent fault condition.

J6 CHECK THE POWERTRAIN CAN (CONTROLLER AREA NETWORK) CIRCUITS FOR AN OPEN

Ignition OFF.

Disconnect GSM C2503.

Disconnect PCM C175T.

Inspect the connectors for damaged or pushed-out terminals.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C2503-13	Courtesy of FORD MOTOR COMPANY	C175T-8
C2503-14	Courtesy of FORD MOTOR COMPANY	C175T-23

Are the resistances less than 3 ohms?

Yes

GO to J7

No	REPAIR the open circuit.

J7 CHECK THE POWERTRAIN CAN (CONTROLLER AREA NETWORK) CIRCUITS FOR A SHORT TO GROUND

Disconnect all other modules on Powertrain CAN. REFER to Wiring Diagrams Electronic Engine Controls - Hybrid for more information.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C2503-13	Courtesy of FORD MOTOR COMPANY	Ground
C2503-14	Courtesy of FORD MOTOR COMPANY	Ground

Are the resistances greater than 10, 000 ohms?

Yes

GO to J8

No	REPAIR the short to ground.

J8 CHECK FOR CORRECT PCM (POWERTRAIN CONTROL MODULE) OPERATION

NOTE: If a GSM self-test is carried out, the driver door must be fully closed. A false P166B DTC may set if the driver door is not fully closed during the self-test.

Ignition OFF.

Disconnect and inspect the GSM, PCM and all related in-line electrical connectors.

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

Connect all disconnected electrical connectors. Make sure they seat and latch correctly.

Using the diagnostic scan tool, clear all diagnostic trouble codes (DTCs).

Road test the vehicle.

Carry out the GSM self-test.

Did DTC U0100: 87 return?

Yes

CHECK for an applicable TSB, GSB, SSM, or FSA. If a service bulletin exists for this concern, discontinue this test and follow bulletin instructions. If none address this concern, Refer to PCM GUIDED ROUTINE TESTING
Internet Explorer version 11 or greater is required to perform this Pinpoint Test.
After programming the new PCM, CARRY OUT the transmission strategy download. REFER to: Transmission Strategy Download .

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.