Pinpoint Test N: DTCs U0151, U1901
Anti-Lock Control
Pinpoint Tests
Pinpoint Test N: DTCs U0151, U1901
Refer to Wiring Diagram Set 42, Vehicle Dynamic Systems for schematic and connector information. Diagrams By Number
Normal Operation
The Restraints Control Module (RCM) measures vehicle yaw rate, roll rate, lateral and longitudinal acceleration and sends the information to the ABS module along dedicated Controller Area Network (CAN) circuits. This dedicated CAN is used only for communication between the RCM and the ABS module. The yaw rate sensor, lateral and longitudinal accelerometers are contained in the RCM.
- DTC U0151 (Lost Communication With Restraints Control Module: Bus Off) - this DTC sets in continuous memory and on-demand when there are expected messages such as yaw rate sensor, lateral and longitudinal accelerometers missing from the RCM for more than 5 seconds.
- DTC U1901 ( CAN Network #2 Communication Bus Fault) - this DTC sets in continuous memory and on-demand when the ABS module detects an open circuit, a short to voltage or a short to ground on one or both of the dedicated CAN bus circuits or the ABS module does not receive information from the RCM.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals, connectors
- RCM
- ABS module
PINPOINT TEST N: DTCs U0151, U1901
WARNING: Never probe the electrical connectors on air bag, Safety Canopy(R) or side air curtain modules. Failure to follow this instruction may result in the accidental deployment of these modules, which increases the risk of serious personal injury or death.
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
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N1 CHECK FOR AN HS-CAN CONCERN WITH THE RCM
- Connect the scan tool.
- Ignition ON.
- NOTE: The network test does not test the dedicated CAN communications between the ABS module and RCM.
- Using the scan tool, carry out the network test.
- Does the RCM pass the network test?
Yes
GO to N2.
No
REFER to Module Communications Network Testing and Inspection, The RCM Does Not Respond To The Scan Tool.
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N2 VERIFY THE RCM PART NUMBER
- Enter the following diagnostic mode on the scan tool: Log Viewer.
- Retrieve and record the RCM part number from the log viewer.
- Check the part number recorded against the number listed in the Ford Catalog Advantage(TM) or equivalent.
- Does the part number on the RCM match the part number listed in the Ford Catalog Advantage(TM) or equivalent?
Yes
GO to N3.
No
INSTALL the correct RCM. REFER to Supplemental Restraint System Service and Repair. CLEAR the DTCs. REPEAT the self-test.
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N3 CHECK THE DEDICATED CAN CIRCUITS FOR A SHORT TO VOLTAGE
- Depower the Supplemental Restraint System (SRS). Refer to Supplemental Restraint System Supplemental Restraint System (SRS) Depowering and Repowering.
- Disconnect: RCM C310B.
- Disconnect: ABS Module C135.
- Ignition ON.
- Measure the voltage between ground and:
- ABS module C135-19, circuit VCA24 (GN/OG), harness side.
- ABS module C135-18, circuit VCA23 (BU/WH), harness side.
- Is any voltage present?
Yes
REPAIR the affected circuit(s) for a short to voltage. CLEAR the DTCs. REPEAT the self-test.
No
GO to N4.
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N4 CHECK THE DEDICATED CAN CIRCUITS FOR A SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between ground and:
- ABS module C135-19, circuit VCA24 (GN/OG), harness side.
- ABS module C135-18, circuit VCA23 (BU/WH), harness side.
- Are the resistances greater than 10,000 ohms?
Yes
GO to N5.
No
REPAIR the affected circuit(s). TEST the system for normal operation.
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N5 CHECK THE DEDICATED CAN CIRCUITS FOR A SHORT TOGETHER
- Measure the resistance between ABS module C135-19, circuit VCA24 (GN/OG), harness side and ABS module C135-18, circuit VCA23 (BU/WH), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to N6.
No
REPAIR the affected circuit(s). CLEAR the DTCs. REPEAT the self-test.
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N6 CHECK THE DEDICATED CAN CIRCUITS FOR AN OPEN
- Measure the resistance between the ABS module C135, harness side and the RCM C310B, harness side as indicated in the following chart:
- Are the resistances less than 5 ohms?
Yes
GO to N7.
No
REPAIR the affected circuit(s). CLEAR the DTCs. CYCLE the ignition key. REPEAT the self-test.
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N7 CHECK FOR CORRECT RCM OPERATION
- Disconnect: RCM C310B.
- Check for:
- corrosion
- pushed-out pins
- spread terminals
- Connect: RCM C310B.
- Make sure the connector is seated correctly, then operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new RCM. REFER to Supplemental Restraint System Service and Repair. CLEAR the DTCs. REPEAT the self-test. If DTC U0151 or U1901 is retrieved again, GO to N8.
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.
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N8 CHECK FOR CORRECT ABS MODULE OPERATION
- Disconnect: ABS Module C135.
- Check for:
- corrosion
- pushed-out pins
- spread terminals
- Connect: ABS Module C135.
- Make sure the connector is seated correctly, then operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new ABS module. REFER to Anti-Lock Brake System (ABS) Module Service and Repair. TEST the system for normal operation.
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.
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