U0121:00

Reconnect the PCM 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 Technical Service Bulletins (TSBs). If a TSB exists for this concern, DISCONTINUE this test and FOLLOW TSB instructions. If no Technical Service Bulletins (TSBs) address this concern, INSTALL a new PCM. For vehicles with the 2.3L EcoBoost (201kW/273PS), REFER to: Powertrain Control Module (PCM) (303-14A Electronic Engine Controls - 2.3L EcoBoost (231kW/314PS), Removal and Installation). For vehicles with the 3.7L Duratec (227kW/301PS), REFER to: Powertrain Control Module (PCM) (303-14B Electronic Engine Controls - 3.7L Duratec (227kW/301PS), Removal and Installation). For vehicles with the 5.0L 32V Ti-VCT, REFER to: Powertrain Control Module (PCM) (303-14C Electronic Engine Controls - 5.0L 32V Ti-VCT/5.0L Ti-VCT V8 (308kW/418PS), Removal and Installation). For vehicles with the 5.2L, REFER to: Powertrain Control Module (PCM) (303-14A Electronic Engine Controls - 5.2L, Removal and Installation).
No	The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues.

Yes

CHECK OASIS for any applicable Technical Service Bulletins (TSBs). If a TSB exists for this concern, DISCONTINUE this test and FOLLOW TSB instructions. If no Technical Service Bulletins (TSBs) address this concern, INSTALL a new PCM. For vehicles with the 2.3L EcoBoost (201kW/273PS), REFER to: Powertrain Control Module (PCM) (303-14A Electronic Engine Controls - 2.3L EcoBoost (231kW/314PS), Removal and Installation).

For vehicles with the 3.7L Duratec (227kW/301PS), REFER to: Powertrain Control Module (PCM) (303-14B Electronic Engine Controls - 3.7L Duratec (227kW/301PS), Removal and Installation).

For vehicles with the 5.0L 32V Ti-VCT, REFER to: Powertrain Control Module (PCM) (303-14C Electronic Engine Controls - 5.0L 32V Ti-VCT/5.0L Ti-VCT V8 (308kW/418PS), Removal and Installation).

For vehicles with the 5.2L, REFER to: Powertrain Control Module (PCM) (303-14A Electronic Engine Controls - 5.2L, Removal and Installation).

The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues.

Normal Operation and Fault Conditions

REFER to: Information and Entertainment System - System Operation and Component Description (415-00B Information and Entertainment System - General Information - Vehicles With: Touchscreen Display, Description and Operation). See Network Message Chart.

DTC Fault Trigger Conditions

Description	Fault Trigger Conditions	DTC Type
U0121:00 Lost Communication With Anti-Lock Brake System (ABS) Control Module: No Sub Type Information	Set by the APIM when network messages are missing from the ABS module for more than 5 seconds with the ignition in RUN.	Continuous

Description

Fault Trigger Conditions

DTC Type

U0121:00 Lost Communication With Anti-Lock

Brake System (ABS) Control Module: No Sub Type Information

Set by the APIM when network messages are missing from the ABS module for more than 5 seconds with the ignition in RUN.

Continuous

DTC

Possible Source

ABS module

PINPOINT TEST AL : U0121:00

AL1 VERIFY THE CUSTOMER'S CONCERN

Ignition ON. Verify if there is an observable symptom present.

Is an observable symptom present?

Source reference 4516

2016 Mustang workshop publication supplied to Mustang Atlas. Original technical text and illustrations; HTML formatting by Mustang Atlas. Source page numbering is retained for traceability. Follow the configuration, revision, warnings, and cross-references in the material. About this edition.