C1251

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CIRCUIT DESCRIPTION
DTC C1251 detects a stripped nut or gear assembly during initialization. During the homing sequence, the piston should reach the top of the bore. Then the ABS motor stalls. If the ABS motor does not stall, the ABS motor must be spinning with little or no resistance. This indicates a nut/screw or gear malfunction.

CONDITIONS FOR SETTING THE DTC
DTC C1251 can only set during initialization. A malfunction exists if the feedback current is less than the command current for a specified period of time.

ACTION TAKEN WHEN THE DTC SETS
^ A malfunction Diagnostic Trouble Code (DTC) stores.
^ The ABS/ETS/TCS disables.
^ The amber ABS/ETS/TCS warning indicator(s) turn on.
^ The red BRAKE warning indicator turns on.

CONDITIONS FOR CLEARING THE DTC
^ The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used.
^ 100 drive cycles pass with no DTC(s) detected.

DIAGNOSTIC AIDS
The following conditions may cause an intermittent malfunction if the conditions exist in a mechanical part of the system:
^ Sticking
^ Binding
^ Slipping

Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction. Refer to the Scan Tool manual for the procedure. DTC C1251 may set after modulator disassembly if the modulator pistons are positioned at the bottom of the modulator piston bore. If DTC C1251 only occurs once and DTC C1264 also occurs, refer to DTC C1264. If intermittent and enhanced diagnostics shows this DTC occurs during ABS, refer to DTC C1264.

Depending on the frequency of the malfunction, a physical inspection of the mechanical parts suspected of causing the malfunction may be necessary.

Clear the DTCs after completing the diagnosis. Test drive the vehicle for three drive cycles in order to verify that the Diagnostic Trouble Code (DTC) does not reset. Use the following procedure in order to complete one drive cycle:
1. Start the vehicle.
2. Drive the vehicle over 16 km/h (10 mph).
3. Stop the vehicle.
4. Turn the ignition to the OFF position.

IMPORTANT: Zero the J 39200 test leads before making any resistance measurements. Refer to the J 39200 user's manual.