Fix P0775: Mechanic’s solutions that WORKED

The OBD2 code P0775 refers to a malfunction in the Pressure Control Solenoid B, indicating an issue within the transmission’s hydraulic system that controls gear shifts. This solenoid is crucial for managing the transmission fluid’s pressure to ensure smooth shifting. Problems here can lead to shifting issues, including harsh or missed shifts, impacting the vehicle’s performance.

P0775 quick overview

Meaning	P0775: Pressure Control Solenoid B Malfunction
Is it serious?	Yes, it can lead to transmission performance issues and potential damage if not addressed.
Possible causes	– Faulty pressure control solenoid – Wiring or circuit problems – Hydraulic issues within the transmission – Faulty transmission control module
How to diagnose?	Inspect the solenoid and circuit for electrical faults. Check transmission fluid for quality and level. Evaluate the hydraulic system for leaks or blockages. Assess TCM for software or hardware issues. Consider mechanical transmission inspection if needed.

How to fix P0775 – learn from mechanics

I looked into P0775 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: Jaguar

Vehicle information 2000 Jaguar S-Type 4.0L

Issue + repair history

• No 5th gear shift and free-wheeling in all gears.
• OBD2 codes: P0735 (5th gear ratio error) and P0775 (pressure solenoid ‘B’ electrical short).
• Solenoid pack replaced three times without success.
• Tested circuit for solenoid continuity and found within specifications.
• Checked valve body components, all appeared to be in good condition.

Other OBD2 Codes + Test Results

• P0735: All 5th gear components used in other gears are okay.
• P0775: Solenoid pack replaced three times, but no resolution.

Mechanic suggestions

• Check harness for short to ground from ECM to transmission.
• Consider the possibility of an ECM problem if harness checks out.
• Mechanical/internal issue suspected; recommend obtaining approval to remove and dissect the transmission for inspection.
• Given the mileage, consider the need for a remanufactured or used transmission.

Final fix

• Discovered broken fingers of the coast clutch that turn the overdrive sprag.
• Solenoid codes were misleading; the mechanical issue with the coast clutch caused the symptoms.
• Transmission disassembly revealed the problem, allowing for the necessary repair.

Case #2: Ford

Vehicle information 2003 Ford Explorer Eddie Bauer 4.6L

Issue + repair history

• OBD2 codes: P0735 (Incorrect Gear 5 Ratio) and P0775 (Pressure Control Solenoid B).
• Loss of overdrive when codes appear.
• Transmission previously checked at a transmission shop two months ago; fluid flushed and filter changed, but no issues were found at that time.

Other OBD2 Codes + Test Results

• P0735: Incorrect Gear 5 Ratio
• P0775: Pressure Control Solenoid B

Mechanic suggestions

• Suspected issue with the OD servo pin bore causing slipping in 2nd and 5th gear and binding on the 2-3 shift.
• Recommended installation of a Ford remanufactured transmission due to the severity of the issue.
• Flex plate and spacer between the crankshaft and flex plate should be inspected for cracks or wear during reassembly.
• Suggested removing the transmission pan to inspect for metal bits; replacement of the transmission is often necessary in such cases.
• Emphasized the importance of checking solenoid B wires at the PCM to ensure proper signal transmission and manually testing the solenoid’s function.
• Highlighted the need to inspect the valve controlled by the solenoid in the valve body to ensure smooth movement.

Final fix

• Consensus points to transmission replacement, but the customer declined the cost involved, resulting in no final resolution.

Case #3: Toyota

Vehicle information 1998 Toyota Sienna LE 3.0L

Issue + repair history

• OBD2 code: P0775 (Pressure Control Solenoid B)
• Transmission does not shift to second gear.
• Replaced valve body with all solenoids from Toyota and flushed transmission, but the issue persisted.
• Checked TPS, mass sensor, and coolant sensor, all operational.
• Noticed that when TPS connector was disconnected, transmission shifted normally.
• Replaced TPS, but problem remained.
• Tested wiring from TPS to ECM and found it to be good.
• Cut brown wire at TPS (ground wire) and transmission shifted normally.

Other OBD2 Codes + Test Results

• P0775: Pressure Control Solenoid B

Mechanic suggestions

• Check all ground wires on transmission, engine, and body to ensure proper grounding.
• P0775 is a solenoid performance code; internal issues or high internal leakage may be causing the problem.
• Rising line pressure may be overcoming an internal leak.
• Suspect transmission or overhaul may be necessary due to high internal leakage, potentially causing clutch failure in second gear.
• Suggests tracing out the hydraulic converter and hydraulic pump in the transmission for damage, which could result in inadequate hydraulic pressure for gear shifting.

Final fix

• Replaced remanufactured transmission, which resolved the issue.

Diagnostic Step	Explanation
Inspect solenoid and circuit	Look for issues that could prevent correct solenoid operation.
Check transmission fluid	Verify fluid is clean and at the right level.
Evaluate hydraulic system	Identify leaks or blockages affecting fluid pressure.
Assess TCM	Check for updates or faults in the transmission’s control module.
Mechanical transmission inspection	If no electrical issues are found, inspect the transmission mechanically.

This streamlined approach to diagnosing P0775 highlights the importance of addressing both the solenoid’s electrical and the transmission’s hydraulic systems to ensure optimal vehicle performance.