What Does C1218 Mean?
The ABS module has detected that the ABS pump motor circuit is either shorted to battery voltage or the motor ground circuit is open. The pump motor is a critical component that generates the hydraulic pressure needed for ABS brake pressure modulation. Without a functioning pump, ABS cannot restore brake pressure after releasing it. The ABS system is disabled and the warning lamp is on.
Safety Warning
ABS is completely disabled. Without pump motor operation, the ABS system cannot restore brake pressure during modulation, which could result in a momentary loss of braking force if any ABS valve were to partially open. Additionally, a shorted pump motor circuit could blow fuses affecting other systems. Repair should be treated as a priority.
Common Causes
30%
Open ground wire or poor ground connection at the ABS pump motor, resulting in an incomplete circuit
25%
Shorted wiring in the pump motor power feed circuit contacting B+ voltage directly, bypassing the module relay control
25%
Failed ABS pump motor with internal winding short to the motor case or open ground brush
10%
ABS pump motor relay failure or relay circuit wiring fault
10%
ABS module internal pump driver circuit failure
Diagnostic Steps
1
Locate the ABS pump motor connector (on the hydraulic modulator assembly). Disconnect it and measure resistance between the motor positive terminal and the motor case ground. Specification is typically 0.5-2 ohms; an open reading suggests a failed motor or open ground path.
2
Check for battery voltage on the pump motor power feed wire with the ignition on. Then verify the ground wire has a solid path to chassis ground (less than 0.5 ohms).
3
Inspect the pump motor ground bolt/terminal for corrosion, looseness, or broken wire. Clean and re-torque. Also check the ground path at the ABS modulator mounting bolts if the motor grounds through the housing.
4
If the motor appears to have a short to voltage, disconnect the pump relay and check if the voltage is still present on the motor feed wire. This isolates whether the short is in the wiring or the relay.
5
Use the scan tool to command the ABS pump motor on. Listen for motor operation and check current draw (typically 3-8 amps). Excessive current or no operation with good voltage and ground points to a failed pump motor.
6
Replace the failed component, clear codes, and verify ABS pump operation and system function during a road test.
Estimated Repair Cost
$200 - $1,500
Parts + labor, varies by vehicle and location
The ABS module has detected that the ABS pump motor circuit is either shorted to battery voltage or the motor ground circuit is open. The pump motor is a critical component that generates the hydraulic pressure needed for ABS brake pressure modulation. Without a functioning pump, ABS cannot restore ...
The most common cause of C1218 (Pump Motor Circuit Shorted to Voltage or Motor Ground Open) is: Open ground wire or poor ground connection at the ABS pump motor, resulting in an incomplete circuit
Typical repair costs for C1218 range from $200 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
ABS is completely disabled. Without pump motor operation, the ABS system cannot restore brake pressure during modulation, which could result in a momentary loss of braking force if any ABS valve were to partially open. Additionally, a shorted pump motor circuit could blow fuses affecting other systems. Repair should be treated as a priority.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1218 to identify the root cause.
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Quick Info
Category
Chassis
System
ABS / Traction Control
Difficulty
Type
Manufacturer
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