Pinpoint Test Ah : DTC U0028, U0037, U0073, U0074
WARNING: This page is about a different car, the 2020 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.
- Refer to TRANSMISSION CONTROLS - 10R80
for schematic and connector information. Refer to MODULE COMMUNICATIONS NETWORK
for schematic and connector information.
Normal Operation and Fault Conditions
The TCM communicates with the PCM on a dedicated CAN bus. The TCM communicates with other vehicle modules over HS-CAN1. A DTC will set if the TCM detects an error with either communication bus.
DTC Fault Trigger Conditions
DTC Description Fault Trigger Condition TCM U0028:00 Vehicle Communication Bus A: No Sub Type Information This DTC illuminates the wrench light in conjunction with U0073. TCM U0037:00 Vehicle Communication Bus B: No Sub Type Information This DTC illuminates the wrench light in conjunction with U0074. TCM U0073:00 Control Module Communication Bus "A" Off: No Sub Type Information This DTC indicates a fault on the vehicle HS-CAN1 bus. TCM U0074:00 Control Module Communication Bus "B" Off: No Sub Type Information This DTC indicates a fault on the powertrain CAN bus. Possible Sources
- Connectors damaged or pushed-out terminals, corrosion, loose wires or ground and missing or damaged seals
- Communication concern
- TCM
- PCM
- AH1 CARRY OUT A TCM (TRANSMISSION CONTROL MODULE) SELF-TEST
- Ignition ON.
- Using a diagnostic scan tool, clear the diagnostic trouble codes (DTCs).
- Road test the vehicle.
- Using a diagnostic scan tool, carry out the TCM self-test.
Is DTC U0028, U0037, U0073 and/or U0074 present?
Yes If any non-network TCM diagnostic trouble codes (DTCs) are present, RESOLVE those first. REFER to the Diagnostic Trouble Code (DTC) Chart .. For U0028 and/or U0073, GO to AH2. For U0037 and/or U0074, GO to AH5 No If the TCM does not respond to the scan tool, REFER to: Communications Network . Otherwise, the concern is not present at this time and may have been set due to high network traffic or an intermittent fault condition. - AH2 CHECK FOR GWM (GATEWAY MODULE A) DIAGNOSTIC TROUBLE CODES (DTCS)
- Using the diagnostic scan tool, carry out the GWM self-test.
Are any GWM diagnostic trouble codes (DTCs) present?
Yes RESOLVE those diagnostic trouble codes (DTCs) first. REFER to: Communications Network . No GO to AH3 - AH3 CHECK THE HS-CAN1 (HIGH-SPEED CONTROLLER AREA NETWORK 1) CIRCUITS FOR AN OPEN
- Ignition OFF.
- Disconnect TCM C1822.
- Disconnect GWM C2431.
- Inspect the connectors for damaged or pushed-out terminals.
Are the resistances less than 3 ohms?
Yes GO to AH4 No REPAIR the circuit. - AH4 CHECK THE HS-CAN1 (HIGH-SPEED CONTROLLER AREA NETWORK 1) CIRCUITS FOR A SHORT TO GROUND
Are the resistances greater than 10, 000 ohms?
Yes GO to AH8 No REPAIR the circuit. - AH5 CHECK FOR PCM (POWERTRAIN CONTROL MODULE) DIAGNOSTIC TROUBLE CODES (DTCS)
- Using the diagnostic scan tool, carry out the KOEO and KOER PCM self-tests.
Are any PCM diagnostic trouble codes (DTCs) present?
Yes RESOLVE those diagnostic trouble codes (DTCs) first. REFER to: Electronic Engine Controls . No GO to AH6 - AH6 CHECK THE CAN (CONTROLLER AREA NETWORK) CIRCUITS FOR AN OPEN
- Ignition OFF.
- Disconnect TCM C1822.
- Disconnect PCM C1915B.
- Inspect the connectors for damaged or pushed-out terminals.
Are the resistances less than 3 ohms?
Yes GO to AH7 No REPAIR the circuit. - AH7 CHECK THE CAN (CONTROLLER AREA NETWORK) CIRCUITS FOR A SHORT TO GROUND
Are the resistances greater than 10, 000 ohms?
Yes GO to AH8 No REPAIR the circuit. - AH8 CHECK FOR CORRECT TCM (TRANSMISSION CONTROL MODULE) OPERATION
- Ignition OFF.
- Disconnect and inspect TCM C1822 and all related in-line electrical connectors.
- 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
- Reconnect TCM C1822 and all related in-line electrical connectors. Make sure they seat and latch correctly.
- Using a diagnostic scan tool, program the TCM with the latest calibration. REFER to: Module Programming .
- Carry out the transmission strategy download. REFER to: Transmission Strategy Download .
- Operate the system and verify the concern is still present.
Is the concern still present?
Yes CHECK OASIS for any applicable service articles: TSB, GSB (general service bulletin), SSM (special service message) or FSA (Field Service Action). 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 TCM. REFER to: Transmission Control Module (TCM) . 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.