Pinpoint Test E: Can Communications Bus Fault

WARNING: This page is about a different car, the 2007 Mercury Mariner and 2007 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Conduct Steps 1 through 7 outlined in Inspection and Verification prior to performing this test.

E1 CHECK FOR DTCs U1900, U0100 AND U0121 SET TOGETHER
- Refer to the results of the 4X4 control module self-test.
- Are DTCs U1900, U0100 and U0121 set together?
1. YES : REFER to MODULE COMMUNICATIONS NETWORK article to continue diagnosis of the communications network.
2. NO : Go to E2.
E2 CHECK FOR DTC U0100
- Refer to the results of the 4X4 control module self-test.
- Is DTC U0100 set, but not U1900?
1. YES : The PCM is not sending any data to the 4X4 control module. REFER to INTRODUCTION - GASOLINE ENGINES or INTRODUCTION -- HYBRID ENGINES article for additional PCM diagnosis.
2. NO : Go to E3.
E3 CHECK FOR DTC U0121
- Refer to the results of the 4X4 control module self-test.
- Is DTC U0121 set, but not U1900?
1. YES : The ABS module is not sending any data to the 4X4 control module. REFER to VEHICLE DYNAMIC SYSTEMS article for additional ABS diagnosis.
2. NO : Go to E4.
E4 CHECK FOR CORRECT 4X4 CONTROL MODULE OPERATION
- Disconnect the 4X4 control module.
- Check for:
  - corrosion.
  - pushed-out pins.
- Connect the 4X4 control module and make sure it seats correctly.
- Operate the system and determine if the concern is still present.
- Is the concern still present?
1. YES : INSTALL a new 4X4 control module. REFER to 4X4 Control Module . CLEAR the DTCs. REPEAT the self-test.
2. NO : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.