C1933

What Does Code C1933 Mean?

The diagnostic trouble code C1933 indicates that the relevant control module (which could be the Powertrain Control Module (PCM), Engine Control Module (ECM), Anti-lock Brake System (ABS) module, Transmission Control Module (TCM), or Body Control Module (BCM), depending on the specific vehicle application and the solenoid’s function) has detected an electrical current reading for a particular solenoid circuit that falls outside its predefined operational range. This typically means the module’s internal monitoring circuitry has measured a current draw that is either significantly higher than expected (suggesting a short circuit or excessively low resistance within the solenoid or its wiring) or significantly lower than expected (indicating an open circuit, high resistance, or a completely failed solenoid). The control module continuously monitors the electrical characteristics of critical solenoids to ensure their proper function and integrity, setting this code when the measured current deviates from manufacturer specifications, impacting the solenoid’s ability to operate correctly.

Common Symptoms

• Illumination of a warning light such as the Malfunction Indicator Lamp (MIL), ABS warning light, Traction Control System (TCS) light, or a specific system warning light (e.g., suspension or steering).
• Reduced or erratic system performance related to the solenoid’s function (e.g., poor braking performance, unstable handling, improper transmission shifts, or HVAC malfunction).
• Unusual noises such as clicking, buzzing, or whining from the vicinity of the affected component, especially if the solenoid is attempting to cycle.
• Noticeable changes in vehicle dynamics or operational characteristics, such as impaired braking feel, suspension stiffness changes, or altered steering effort.
• In some cases, the vehicle may enter a “limp mode” to prevent further damage.

What Causes the Code C1933?

• Faulty Solenoid: The solenoid itself may have an internal electrical fault, such as a shorted coil winding, an open circuit within the coil, or excessive internal resistance due to wear or damage.
• Wiring Harness Issues:
  • Open Circuit: A broken wire in the solenoid’s power or ground circuit, preventing current flow.
  • Short to Ground: The solenoid’s positive circuit wire making unintended contact with chassis ground, leading to excessive current draw.
  • Short to Voltage: The solenoid’s ground circuit or signal wire making unintended contact with a constant power source, causing incorrect current.
  • High Resistance: Corrosion, loose terminals, or damaged insulation in the wiring or connectors leading to a voltage drop and insufficient current.
• Corroded or Damaged Connectors: Poor electrical contact at the solenoid or control module connectors due to corrosion, bent pins, or insufficient terminal tension.
• Control Module Malfunction: Less common, but an internal failure within the control module’s driver circuit or monitoring circuitry could lead to incorrect current output or misinterpretation of feedback.
• External Contamination/Mechanical Binding: If the solenoid operates within a fluid or mechanical system, contamination or physical binding could cause the solenoid plunger to stick, leading to abnormal current demands.

How to Diagnose and Troubleshoot

Diagnosis of C1933 requires a systematic approach using a suitable diagnostic scan tool and a digital multimeter (DMM).

1. Initial Scan Tool Diagnosis:
   • Connect an OBD-II scan tool and confirm the presence of C1933. Check for any related or accompanying diagnostic trouble codes that might provide further clues about the affected system.
   • Review Freeze Frame Data associated with C1933. This data captures engine and vehicle operating parameters at the moment the code was set, which can be invaluable in replicating the conditions under which the fault occurred.
   • If available, observe live data parameters related to the solenoid in question (e.g., commanded state, actual current feedback) to see if the control module is attempting to activate it and what current it is reporting.
2. Visual Inspection:
   • Locate the specific solenoid mentioned in the vehicle’s service information for code C1933.
   • Carefully inspect the wiring harness leading to the solenoid and its connector for any signs of physical damage, chafing, cuts, pinches, or rodent damage.
   • Examine the solenoid connector and its mating harness connector for corrosion, bent pins, loose terminals, or signs of moisture intrusion. Ensure connections are secure.
3. Electrical Testing with a Digital Multimeter (DMM):
   • Solenoid Resistance Test: Disconnect the solenoid’s electrical connector. Using a DMM set to ohms, measure the resistance across the solenoid’s terminals. Compare this reading to the manufacturer’s specifications (found in service manuals). An “Open Limit” (OL) reading indicates an open circuit, while a reading significantly lower than specified suggests a shorted coil. Deviations outside the specified range indicate an internal solenoid fault.
   • Voltage Supply Test: With the solenoid disconnected and the ignition ON (and potentially the relevant system activated, if safe and applicable), use the DMM set to DC volts to check for proper voltage supply at the solenoid’s harness connector (usually battery voltage or a controlled voltage from the module).
   • Ground Circuit Integrity Test: Verify a strong ground connection at the solenoid’s harness connector. With the ignition OFF, measure resistance between the ground terminal of the harness connector and a known good chassis ground point. Resistance should be very low (typically less than 0.5 ohms). Alternatively, with the solenoid connected, use a test light connected to battery positive to probe the ground side of the solenoid (if it’s a switched ground circuit from the module); the light should illuminate brightly.
   • Continuity and Short Circuit Test (Wiring Harness): Disconnect both the solenoid and the control module’s connector. Use the DMM set to ohms to test for continuity between the corresponding pins of the control module and the solenoid connectors for both the power and ground/signal wires. Resistance should be minimal (typically less than 0.5 ohms). Also, test each wire for shorts to ground and shorts to voltage by checking continuity between the wire and chassis ground, and between the wire and a known power source wire.
4. Load Testing (if needed): If resistance and voltage tests are inconclusive, a load test on the wiring may be necessary. Use a test light or appropriate incandescent bulb in place of the solenoid to check if the circuit can carry sufficient current without excessive voltage drop.

Recommended Repairs and Solutions

Based on the diagnostic findings, the following repairs are typically recommended:

• Replace the Faulty Solenoid: If the solenoid’s internal resistance measurements are outside specifications or if it shows signs of mechanical binding or damage, replacement is the most direct solution. Always use an OEM-equivalent or genuine manufacturer part for optimal performance and longevity.
• Repair or Replace Wiring Harness: If an open circuit, short to ground, short to voltage, or high resistance is identified in the wiring harness, the damaged section must be repaired or the entire harness replaced. For repairs, use appropriate automotive-grade wiring, connectors, and heat-shrink tubing. Avoid quick splices that can lead to future issues.
• Clean or Repair Connectors: If corrosion or poor terminal tension is found in the connectors, carefully clean the terminals using electrical contact cleaner and a small brush. If terminals are significantly damaged or corroded, replace the individual pins or the entire connector housing. Ensure all connections are secure and weatherproofed.
• Replace the Control Module: This should be considered a last resort. If all other components (solenoid, wiring, and connectors) have been thoroughly tested and confirmed to be functioning correctly, and the control module is verified to have an internal driver or monitoring circuit fault, replacement may be necessary. After installing a new control module, it will typically require programming or calibration to the vehicle using manufacturer-specific diagnostic tools.
• Address External Factors: If the solenoid operates in a fluid, ensure the fluid is clean and at the correct level, as contamination can sometimes lead to solenoid malfunctions. For hydraulic systems (e.g., ABS), a system bleed procedure may be required after component replacement.