Diagnostic Test

WARNING: This page is about a different car, the 2005 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

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
1. Go To step 2).
No
1. Refer ABS-INTERMITTENT CONDITION .
2. Perform ABS VERIFICATION TEST - VER 1 .
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
1. Repair as necessary.
2. Perform ABS VERIFICATION TEST - VER 1 .
No
1. Go To step 3).
3) CHECK THE (D65) CAN C (+) BUS AND (D64) CAN C (-) BUS CIRCUITS FOR A SHORT TOGETHER

Fig 1: Checking CAN C (+) BUS Circuit & CAN C (-) BUS Circuit
Courtesy of DAIMLERCHRYSLER CORP.

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
1. Repair the (D65) CAN C (+) BUS and the (D64) CAN C (-) BUS circuits for a short together.
2. Perform ABS VERIFICATION TEST - VER 1 .
No
1. Go To step 4).
4) CHECK THE (D65) CAN C (+) BUS CIRCUIT FOR A SHORT TO GROUND

Fig 2: Checking CAN C (+) BUS Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the Powertrain Control Module harness connector.

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

Is the resistance below 5.0 ohms?

Yes
1. Repair the (D65) CAN C (+) BUS circuit for a short to ground.
2. Perform ABS VERIFICATION TEST - VER 1 .
No
1. Go To step 5).
5) CHECK THE (D65) CAN C (+) BUS CIRCUIT FOR A SHORT TO VOLTAGE

Fig 3: Checking CAN C (+) BUS Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition on.

Measure the voltage of the (D65) CAN C (+) BUS circuit.

Is there any voltage present?

Yes
1. Repair the (D65) CAN C (+) BUS circuit for a short to voltage.
2. Perform ABS VERIFICATION TEST - VER 1 .
No
1. Go To step 6).
6) CHECK THE (D65) CAN C (+) BUS CIRCUIT FOR AN OPEN CIRCUIT

Fig 4: Checking CAN C (+) BUS Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Measure the resistance of the (D65) CAN C (+) Bus circuit.

Is the resistance below 5.0 ohms?

Yes
1. Go To step 7).
No
1. Repair the (D65) CAN C (+) BUS circuit for an open circuit.
2. Perform ABS VERIFICATION TEST - VER 1 .
7) CHECK THE (D64) CAN C (-) BUS CIRCUIT FOR A SHORT TO GROUND

Fig 5: Checking CAN C (-) BUS Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

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

Is the resistance below 5.0 ohms?

Yes
1. Repair the (D64) CAN C (-) BUS circuit for a short to ground.
2. Perform ABS VERIFICATION TEST - VER 1 .
No
1. Go To step 8).
8) CHECK THE (D64) CAN C (-) BUS CIRCUIT FOR A SHORT TO VOLTAGE

Fig 6: Checking CAN C (-) BUS Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition on.

Measure the voltage of the (D64) CAN C (+) BUS circuit.

Is there any voltage present?

Yes
1. Repair the (D64) CAN C (-) BUS circuit for a short to voltage.
2. Perform ABS VERIFICATION TEST - VER 1 .
No
1. Go To step 9).
9) CHECK THE (D64) CAN C (-) BUS CIRCUIT FOR AN OPEN CIRCUIT

Fig 7: Checking CAN C (-) BUS Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Measure the resistance of the (D64) CAN C (-) Bus circuit.

Is the resistance below 5.0 ohms?

Yes
1. Replace the Powertrain Control Module in accordance with the Service Information.
2. Perform ABS VERIFICATION TEST - VER 1 .
No
1. Repair the (D64) CAN C (-) BUS circuit for an open circuit.
2. Perform ABS VERIFICATION TEST - VER 1 .