C121C

C121C-TORQUE REQUEST SIGNAL DENIED








When Monitored:

With the ignition on.

Set Condition:

When the Anti-Lock Brake Module indicates if engine management relevant for Automatic Yaw Control/Traction Control System control can be accomplished.

Possible Causes

TERMINAL/CONNECTOR/WIRING HARNESS DAMAGE
(D65) CAN C (+) BUS AND (D64) CAN C (-) BUS CIRCUITS SHORTED TOGETHER
(D65) CAN C (+) BUS CIRCUIT SHORTED TO VOLTAGE GROUND OR OPEN
(D64) CAN C (-) BUS CIRCUIT SHORTED TO VOLTAGE GROUND OR OPEN
POWERTRAIN CONTROL MODULE

Diagnostic Test

1. CHECK FOR A DTC C121C-TORQUE REQUEST SIGNAL DENIED





NOTE: This DTC must be active for the results of this test to be valid.

Turn the ignition on.

With the scan tool read and record DTC's.

With the scan tool read and record Freeze Fame information.

With the scan tool erase DTC's.

Cycle the ignition switch from off to on.

With the scan tool read and record DTC's.

Does the scan tool display: C121C-TORQUE REQUEST SIGNAL DENIED?

Yes

^ Go To 2

No

^ Refer to the INTERMITTENT CONDITION diagnostic procedure. Testing and Inspection.
^ Perform ABS VLRIFICATION TEST - VER 1. ABS Verification Test.

2. CHECK THE TERMINALS/CONNECTORS/WIRING HARNESS FOR DAMAGE





Check all related wiring for bruised, chafed, pierced, or partially broken wires. Check all related connectors for broken, bent, pushed out, or corroded terminals.

Were any problems found?

Yes

^ Repair as necessary.
^ Perform ABS VLRIFICATION TEST - VER 1. ABS Verification Test.

No

^ Go To 3

3. CHECK THE (D65) CAN C (+) BUS AND (D64) CAN C (-) BUS CIRCUITS FOR A SHORT TOGETHER





Turn the ignition off.

Disconnect the Anti-Lock Brake Module harness connector.

Measure the resistance between the (D65) CAN C (+) BUS circuit and the (D64) CAN C (-) BUS circuit.

Is the resistance below 150 ohms?

Yes

^ Repair the (D65) CAN C (+) BUS and the (D64) CAN C (-) BUS circuits for a short together.
^ Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test.

No

^ Go To 4

4. CHECK THE (D65) CAN C (+) BUS CIRCUIT FOR A SHORT TO GROUND





Turn the ignition off.

Disconnect the Anti-Lock Brake Module harness connector.

Disconnect the Powertrain Control Module harness connector.

Turn the ignition on.

Using a 12-volt test light connected to 12-volts, check the (D65) CAN C (+) BUS circuit.

Does the test light illuminate brightly?

Yes

^ Repair the (D65) CAN C (+) BUS circuit for a short to ground.
^ Perform ABS VLRIFICATION TEST - VER 1. ABS Verification Test.

No

^ Go To 5

5. CHECK THE (D65) CAN C (+) BUS CIRCUIT FOR A SHORT TO VOLTAGE





Turn the ignition off.

Disconnect the Anti-Lock Brake Module harness connector.

Disconnect the Powertrain Control Module harness connector.

Turn the ignition on.

Using a 12-volt test light connected to ground, check the (D65) CAN C (+) BUS circuit.

Does Cthe test light illuminate brightly?

Yes

^ Repair the (D65) CAN C (+) BUS circuit for a short to voltage.
^ Perform ABS VLRIFICATION TEST - VER 1. ABS Verification Test.

No

^ Go To 6

6. CHECK THE (D65) CAN C (+) BUS CIRCUIT FOR AN OPEN CIRCUIT





Turn the ignition off.

Disconnect the Anti-Lock Brake Module harness connector.

Disconnect the Powertrain Control Module harness connector.

Measure the resistance of the (D65) CAN C (+) Bus circuit between the Anti-lock Brake Module and the Powertrain Control Module.

Is the resistance below 5.0 ohms?

Yes

^ Go To 7

No

^ Repair the (D65) CAN C (+) BUS circuit for an open circuit.
^ Perform ABS VLRIFICATION TEST - VER 1. ABS Verification Test.

7. CHECK THE (D64) CAN C (-) BUS CIRCUIT FOR A SHORT TO GROUND





Turn the ignition off.

Disconnect the Anti-Lock Brake Module harness connector.

Disconnect the Powertrain Control Module harness connector.

Turn the ignition on.

Using a 12-volt test light connected to 12-volts, check the (D64) CAN C (-) BUS circuit.

Does the test light illuminate brightly?

Yes

^ Repair the (D64) CAN C (-) BUS circuit for a short to ground.
^ Perform ABS VLRIFICATION TEST - VER 1. ABS Verification Test.

No

^ Go To 8

8. CHECK THE (D64) CAN C (-) BUS CIRCUIT FOR A SHORT TO VOLTAGE





Turn the ignition off.

Disconnect the Anti-Lock Brake Module harness connector.

Disconnect the Powertrain Control Module harness connector.

Turn the ignition on.

Using a 12-volt test light connected to ground, check the (D64) CAN C (+) BUS circuit.

Does the test light illuminate brightly?

Yes

^ Repair the (D64) CAN C (-) BUS circuit for a short to voltage.
^ Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test.

No

^ Go To 9

9. CHECK THE (D64) CAN C (-) BUS CIRCUIT FOR AN OPEN CIRCUIT





Turn the ignition off.

Disconnect the Anti-Lock Brake Module harness connector.

Disconnect the Powertrain Control Module harness connector.

Measure the resistance of the (D64) CAN C (-) Bus circuit between the Anti-lock Brake Module and the Powertrain Control Module.

Is the resistance below 5.0 ohms?

Yes

^ Replace the Powertrain Control Module.
^ Perform ABS VLRIFICATION TEST - VER 1. ABS Verification Test.

No

^ Repair the (D64) CAN C (-) BUS circuit for an open circuit.
^ Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test.