C1924

What Does Code C1924 Mean?

DTC C1924 indicates a detected short to ground within the output circuit of the Variable Assist Power Steering (VAPS) solenoid actuator. The VAPS system, typically controlled by the Powertrain Control Module (PCM) or a dedicated Power Steering Control Module (PSCM), dynamically adjusts the power steering assist level based on vehicle speed and other driving parameters. The VAPS solenoid actuator, often an electronically controlled valve on the power steering pump or steering rack, modulates hydraulic fluid flow or pressure to achieve this variable assist.

The control module continuously monitors the electrical integrity of the VAPS solenoid’s control circuit. When the module attempts to energize the solenoid or expects a specific voltage/current signature on its output circuit, it observes an electrical short to ground. This means the circuit’s voltage is unexpectedly low or at zero potential, indicating that the current intended for the solenoid is being diverted directly to the vehicle’s chassis or another ground source before reaching or passing through the solenoid’s winding. This prevents the VAPS solenoid from functioning correctly, leading to a loss or malfunction of the variable assist feature.

Common Symptoms

• Inconsistent Steering Effort: The most prevalent symptom is a noticeable change in steering feel. This can manifest as excessively stiff steering at low speeds or while parking, and potentially over-assisted (too light) steering at higher speeds, as the system fails to vary assist as intended.
• “Service Power Steering” Warning Light: A warning message or an illuminated power steering indicator on the instrument cluster will typically appear, signaling a fault in the power steering system.
• Difficulty Steering: Increased physical effort is required to turn the steering wheel, particularly during low-speed maneuvers.
• Intermittent Power Steering Loss: In some cases, the power steering assist may become erratic, working sometimes and failing at others, depending on the nature of the short circuit.

What Causes the Code C1924?

• Damaged Wiring Harness: The most frequent cause is damage to the VAPS solenoid’s electrical wiring, such as chafing, pinching, or cuts, which causes the insulated wire to make direct contact with a grounded metal component of the vehicle.
• Faulty VAPS Solenoid Actuator: An internal short circuit within the solenoid itself, where the winding insulation breaks down, causing the coil to short directly to the solenoid’s metal housing (which is typically grounded).
• Corroded Electrical Connectors: Water intrusion or exposure to corrosive elements can lead to corrosion within the VAPS solenoid connector or related harness connectors, creating an unintended electrical path to ground.
• Improperly Routed Harness: The wiring harness leading to the VAPS solenoid may be routed incorrectly, causing it to rub against sharp edges, hot engine components, or moving parts, eventually wearing through the insulation and creating a short.
• Faulty Power Steering Control Module (PSCM) or PCM: While less common, an internal short within the control module’s VAPS driver circuit can also trigger this code. This should be considered only after thoroughly ruling out external wiring and solenoid faults.

How to Diagnose and Troubleshoot

Diagnosing C1924 requires systematic electrical testing to pinpoint the exact location of the short to ground. Always begin with a thorough visual inspection.

1. Visual Inspection:
   • Locate the VAPS solenoid actuator, which is typically mounted on the power steering pump, steering rack, or an inline hydraulic control valve.
   • Carefully inspect the entire wiring harness leading from the control module (PCM/PSCM) to the VAPS solenoid. Look for any signs of chafing, pinching, melting, or cuts in the insulation. Pay close attention to areas where the harness passes through firewalls, along frame rails, or near exhaust components.
   • Examine the electrical connector at the VAPS solenoid for bent pins, corrosion, loose connections, or signs of water intrusion.
2. Scan Tool Analysis:
   • Connect an OBD-II scanner and verify C1924 is present. Check for any related power steering or communication codes.
   • Clear the code and perform a test drive to see if it immediately returns, which can indicate a hard short.
   • If available, monitor VAPS solenoid live data parameters (e.g., commanded state, duty cycle, feedback voltage) to observe its behavior while commanding it via a bi-directional scan tool.
3. Digital Multimeter (DMM) Testing (with battery disconnected):
   • Isolate the Circuit: Disconnect the vehicle’s battery to prevent electrical damage. Disconnect the electrical connector from the VAPS solenoid actuator.
   • Test for Short to Ground in Wiring: Using a DMM set to ohms, measure the resistance between the VAPS solenoid’s control wire (at the harness connector, leading back to the control module) and a known good chassis ground. There should be infinite resistance (an open circuit). If you read very low resistance (near 0 ohms), the wiring harness itself is shorted to ground. Systematically flex and manipulate the harness while observing the DMM to help locate intermittent shorts.
   • Test VAPS Solenoid Internal Short: With the solenoid still disconnected from the harness, measure the resistance between each of the solenoid’s terminals and its metal housing (if applicable, as a ground reference). An ideal solenoid should show a specific resistance value across its terminals (check service manual specifications) and infinite resistance to its housing. If any terminal shows very low resistance to the housing, the solenoid is internally shorted.
4. Power and Ground Supply Check (with battery reconnected, carefully):
   • Reconnect the battery. With the ignition on (engine off), carefully check for proper power supply to the VAPS solenoid connector (if it has a dedicated power feed, typically B+ or switched ignition voltage). Use the DMM to measure voltage.
   • Check for proper ground reference at the connector if the module supplies a switched ground.
5. Control Module Output Test (Advanced):
   • If the wiring and solenoid test good, carefully back-probe the VAPS output circuit at the control module connector. Using a bi-directional scan tool, command the VAPS solenoid on and off while observing the voltage output from the module. If the module’s output remains consistently low or at zero volts when commanded active, and the external circuit is confirmed good, the control module itself may be faulty.

Recommended Repairs and Solutions

Once the source of the short to ground has been identified through diagnosis, the appropriate repair can be made:

• Repair or Replace Damaged Wiring: If the wiring harness is found to be chafed, cut, or otherwise shorted, the damaged section must be repaired. Use high-quality, appropriate gauge wire, solder connections, and seal them with heat-shrink tubing to ensure a durable repair. Ensure the harness is re-routed correctly and secured to prevent future damage. For extensive or multiple points of damage, replacing the entire harness section is often the more reliable long-term solution.
• Replace VAPS Solenoid Actuator: If testing confirms an internal short within the VAPS solenoid itself, the actuator must be replaced. This typically involves disconnecting hydraulic lines (if applicable) and electrical connections. After replacement, it is critical to ensure the power steering system is properly bled of air according to manufacturer specifications to prevent pump damage or noisy operation.
• Clean or Replace Corroded Connectors: If corrosion is the culprit, clean the connector terminals using an electrical contact cleaner and a small wire brush. If the corrosion is severe, or if pins are bent or damaged, replace the affected connector or the harness pigtail section.
• Control Module Replacement: Only consider replacing the Power Steering Control Module (PSCM) or PCM as a last resort, after all other external components (wiring, solenoid) have been thoroughly tested and confirmed good. Module replacement often requires programming or calibration specific to the vehicle, which may require specialized diagnostic equipment.
• Post-Repair Verification: After completing any repair, clear the DTCs with a scan tool. Perform a thorough test drive under various driving conditions (low speed, high speed) to confirm that the code does not return and that the variable assist power steering system is functioning correctly and smoothly. Check power steering fluid levels and top off if necessary, bleeding the system again if any hydraulic lines were opened.