Fix P0796: Mechanic’s solutions that WORKED

The P0796: Pressure Control Solenoid C Performance or Stuck Off indicates a problem with the Pressure Control Solenoid C in the transmission. This solenoid helps regulate the hydraulic pressure for shifting gears. If it’s not performing correctly or gets stuck, it can lead to transmission issues, such as harsh shifting or failure to shift.

P0796 quick overview

Meaning	P0796: Pressure Control Solenoid C Performance or Stuck Off
Is it serious?	This code is serious as it indicates a problem with the transmission’s pressure control, potentially leading to poor shifting or transmission damage.
Possible causes	– Faulty pressure control solenoid – Transmission fluid issues (low level, dirty, or wrong type) – Hydraulic blockages within the transmission – Faulty transmission control module – Wiring or electrical connection problems
How to diagnose?	Check Transmission Fluid: Verify the fluid level is correct and the fluid is in good condition. Inspect Solenoid: Examine the pressure control solenoid for correct operation and resistance. Scan for Additional Codes: Use a diagnostic tool to find any related transmission codes. Evaluate Electrical Connections: Check the wiring and connectors for damage or loose connections. Conduct Pressure Tests: Perform hydraulic pressure tests in the transmission. Assess Control Module: Check the transmission control module for faults or errors.

How to fix P0796 – learn from mechanics

I looked into P0796 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Ford

Vehicle Information: 2001 Ford Explorer XLS, 4.0L

Issue + Repair History:

• Transmission O/D light flashing when put into drive; hard shifting.
• Code 796 for pressure solenoid C.
• Conducted bench test function of scanner, found no voltage change at transmission plug for solenoids A, B, C.
• 4×4 module not working for a year; no communication to module found.

Other OBD2 Codes + Test Results:

• P0796 – PC solenoid C performance or stuck off.

Suggestions to Fix Issue:

• Check the pressure control solenoid and circuit.
• Consider refreshing the unit with a new converter and clear all codes.
• Ensure the right module is used and functioning correctly.
• Replace the solenoid pack if necessary.

Final Fix:

• The Snap-on Solus scanner was not correctly bench testing the solenoids.
• Conducted pin testing from the ECM side and found an open on PC solenoid C.
• Replaced the solenoid pack and filter on the truck.
• Replaced the 4×4 module.
• Vehicle now shifts correctly, and 4×4 works properly.

Case #2: Jaguar

Vehicle Information: 2001 Jaguar S-Type, 3.0L

Issue + Repair History:

• Vehicle previously had a transmission failure.
• Another shop replaced the transmission with a used one.
• After replacement, the car would not move in any gear.
• The previous shop suggested that the transmission might need programming or coding.
• Current diagnostic codes: P0796, P0713, P0743, P1746.

Suggestions to Fix Issue:

• Check if the transmission is properly plugged in; these codes indicate electrical issues.
• No Transmission Control Module (TCM) in this model, so no coding is needed.
• Verify fluid level and connections to the transmission.
• Consider internal transmission faults if electrical aspects are fine.
• If there’s reverse but no forward gears, the forward drum or snap ring might have failed.

Final Fix:

• Installed used transmission

Case #3: Chevrolet

Vehicle Information: 2011 Chevrolet Cruze LS, 1.8L

Issue + Repair History:

• No forward motion, but reverse works perfectly.
• Initially, no diagnostic codes, but later showed P2723 (Pressure Control Solenoid Valve 5 stuck off).
• Fluid was very dark; transmission flushed but issue persisted.
• Suspected solenoid problem, but unclear why no codes for lower gears appeared.

Other OBD2 Codes + Test Results:

• P2723: Pressure Control Solenoid Valve 5 stuck off.
• P0796

Suggestions to Fix Issue:

• Check for transmission electrical issues.
• Investigate solenoid functionality and connections.
• Consider valve body or clutch piston issues.
• Evaluate the need for further diagnostic time or replacement of transmission unit.

Final Fix:

• Found and followed Bulletin #16-NA-092 regarding transmission issues.
• Replaced and programmed the Transmission Control Module (TCM), resolving the issue.

Case #4: Honda

Vehicle Information: 2007 Honda Odyssey EX-L, 3.5L

Issue + Repair History:

• Clutch pressure control valve C stuck off, causing a 5-second delay going into reverse.
• Upshifts were fine, but a delay was persistent.
• Transmission fluid slightly dark, but no metal or clutch material found.
• After tests and a short drive, the code P0796 reappeared.
• Transmission slightly slipping, customer opted for a fluid flush to extend its life.

Other OBD2 Codes + Test Results:

• P0796: Clutch pressure control valve C stuck off.

Suggestions to Fix Issue:

• Test voltage and amperage at PCM/TCM to solenoid.
• Conduct fluid pressure testing using an oil pressure gauge on test ports.
• Inspect for any internal transmission issues like a sticking valve.
• Consider if there is a delay from the TCM, suggesting a TCM problem or incorrect voltage/amperage.
• Drain and fill transmission fluid, using Honda-specific ATF.
• Check for any internal issues causing low pressure on the hydraulic circuit.

Final Fix:

• After extensive testing with a lab scope, found that the CPC C worked perfectly.
• Cleared and tested the code, which did not return.
• Decided on a transmission flush due to slight slipping, with the expectation that the transmission may eventually need more extensive repairs or replacement.

Case #5: Lexus

Vehicle Information: 2003 Lexus ES300, 3.0L

Issue + Repair History:

• Initially had P0746 shift solenoid A error; shift solenoid replaced but issue persisted.
• Replaced transmission but the problem continued with no 1st, 3rd, or 5th gear, and codes P0746 and P0796.
• Seemed to be in limp mode with just 2nd and 4th gear, and had issues shifting between gears.

Other OBD2 Codes + Test Results:

• P0746: Shift Solenoid A
• P0796: Pressure Control Solenoid C Performance or Stuck Off

Suggestions to Fix Issue:

• Check the Transmission Control Module (TCM); possibly needs replacement or reflash.
• Inspect ground wires on the back of the intake, even if they are tight, clean them.
• Consider possible wiring issues or PCM problem.
• If there were debris in the pan initially, it might indicate a failed transmission.
• Check all wires and connectors in the harness for issues.

Final Fix:

• The issue was resolved by replacing the PCM (Powertrain Control Module).
• All engine grounds were checked and found clean, but were cleaned again as a precaution.
• The wiring harness was inspected and found to be problem-free.
• After PCM replacement, the car shifted smoothly.

Takeaway Advice	Description of Diagnostic Step
Inspect Transmission Solenoids	Check operation and electrical resistance of transmission solenoids.
Check Fluid Condition and Level	Ensure transmission fluid is at correct level and in good condition.
Scan for Additional Codes	Use a diagnostic scanner to check for other related codes.
Inspect Wiring and Connectors	Check wiring harness and connectors for damage, wear, or loose connections.
Consider Mechanical Issues	Evaluate for internal mechanical problems in the transmission, such as worn clutches.
Perform Pressure Tests	Conduct hydraulic pressure tests for correct pressure maintenance in various gears.
Evaluate Control Module	Assess the condition and functionality of the transmission control module.