P1904: Pressure Control Solenoid "C" Open Circuit

Definition

The OBD2 code P1904 indicates that there is an open circuit in the Pressure Control Solenoid "C," which means the solenoid is not receiving the proper electrical signal or is malfunctioning, potentially affecting transmission fluid pressure control

Common causes

Faulty pressure control solenoid "C"
Open or damaged wiring harness
Poor electrical connections
Failed transmission control module (TCM)
Short circuit in the solenoid circuit
Corroded connectors
Blown fuse related to the solenoid circuit
Internal transmission failure

Common misdiagnoses

Faulty pressure control solenoid
Wiring issues or short circuits
Transmission fluid issues (low fluid, contamination)
Faulty transmission control module (TCM)
Incorrectly installed or damaged connectors
Internal transmission failure
Other solenoid failures (A, B, etc.)
Sensor malfunctions (e.g., transmission fluid temperature sensor)

Troubleshooting steps

1. Check for Additional Codes

Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide more context and help identify related issues
2. Inspect Wiring and Connectors
3. Visually inspect the wiring harness and connectors associated with the Pressure Control Solenoid "C." Look for signs of damage, such as frayed wires, corrosion, or loose connections
4. Ensure that the connectors are securely attached and free of dirt or debris
5. Test the Solenoid
6. If accessible, test the solenoid itself for continuity using a multimeter. Refer to the vehicle's service manual for the specific resistance values
7. If the solenoid is open (infinite resistance), it may need to be replaced
8. Check Power and Ground
9. Use a multimeter to check for power and ground at the solenoid connector. Ensure that the solenoid is receiving the correct voltage when the ignition is on and the engine is running
10. If there is no power or ground, trace the wiring back to the source to identify any breaks or shorts
11. Inspect the Transmission Control Module (TCM)
12. The TCM controls the solenoid operation. Check for any issues with the TCM, including software updates or faults
13. If necessary, perform a reset or reprogram the TCM according to the manufacturer's specifications
14. Check for Fluid Issues
15. Inspect the transmission fluid level and condition. Low or contaminated fluid can cause solenoid issues
16. If the fluid is dirty or burnt, consider performing a transmission fluid change
17. Perform a Visual Inspection of the Transmission
18. Look for any signs of leaks or damage to the transmission that could affect solenoid operation
19. Consult Technical Service Bulletins (TSBs)
20. Check for any TSBs related to the P1904 code for your specific vehicle make and model. Manufacturers may have known fixes or recommendations
21. Clear Codes and Test Drive
22. After performing repairs or replacements, clear the trouble codes and take the vehicle for a test drive to see if the code returns
23. Seek Professional Help
24. If the issue persists after following these steps, it may be necessary to consult a professional mechanic or transmission specialist for further diagnosis. By following these troubleshooting steps, you can systematically identify and resolve the issue related to the P1904 code

Definition

Common causes

Common misdiagnoses

Troubleshooting steps

1. Check for Additional Codes

2. Inspect Wiring and Connectors

3. Visually inspect the wiring harness and connectors associated with the Pressure Control Solenoid "C." Look for signs of damage, such as frayed wires, corrosion, or loose connections

4. Ensure that the connectors are securely attached and free of dirt or debris

5. Test the Solenoid

6. If accessible, test the solenoid itself for continuity using a multimeter. Refer to the vehicle's service manual for the specific resistance values

7. If the solenoid is open (infinite resistance), it may need to be replaced

8. Check Power and Ground

9. Use a multimeter to check for power and ground at the solenoid connector. Ensure that the solenoid is receiving the correct voltage when the ignition is on and the engine is running

10. If there is no power or ground, trace the wiring back to the source to identify any breaks or shorts

11. Inspect the Transmission Control Module (TCM)

12. The TCM controls the solenoid operation. Check for any issues with the TCM, including software updates or faults

13. If necessary, perform a reset or reprogram the TCM according to the manufacturer's specifications

14. Check for Fluid Issues

15. Inspect the transmission fluid level and condition. Low or contaminated fluid can cause solenoid issues

16. If the fluid is dirty or burnt, consider performing a transmission fluid change

17. Perform a Visual Inspection of the Transmission

18. Look for any signs of leaks or damage to the transmission that could affect solenoid operation

19. Consult Technical Service Bulletins (TSBs)

20. Check for any TSBs related to the P1904 code for your specific vehicle make and model. Manufacturers may have known fixes or recommendations

21. Clear Codes and Test Drive

22. After performing repairs or replacements, clear the trouble codes and take the vehicle for a test drive to see if the code returns

23. Seek Professional Help

24. If the issue persists after following these steps, it may be necessary to consult a professional mechanic or transmission specialist for further diagnosis. By following these troubleshooting steps, you can systematically identify and resolve the issue related to the P1904 code