Fix P0755: Mechanic’s solutions that WORKED

The OBD2 code P0755 is an indication that there’s a malfunction in the electrical circuit of Shift Solenoid B in the transmission. This solenoid is responsible for controlling fluid flow to activate the appropriate gear. When it fails or the circuitry has issues, it can lead to symptoms such as the transmission not shifting properly, being stuck in a gear, or experiencing erratic shifts. These cases from Nissan, Ford, and Chrysler vehicles illustrate common troubleshooting steps and solutions for resolving this code.

P0755 quick overview

Meaning	P0755: Shift Solenoid B Circuit Malfunction
Is it serious?	Yes, it can impact drivability and may cause the transmission to enter a limp mode to prevent further damage.
Possible causes	– Faulty shift solenoid B – Wiring or connector issues in the solenoid circuit – ECM/PCM issues – Grounding problems
How to diagnose?	Check the solenoid’s grounding and wiring for integrity Inspect the ECM for known issues, especially in models with recalls Test the solenoid’s operation directly from the TCM/PCM Clear codes and perform an extended test drive to monitor for recurrence Inspect wiring harness for damage or breaks

How to fix P0755 – learn from mechanics

I looked into P0755 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: Nissan

Vehicle Information 2002 Nissan Sentra CA 1.8L

Issue + Repair History

• Transmission not shifting, no voltage sent to solenoids A or B during acceleration.
• TCC solenoid buzzes in park while opening the throttle.
• Transmission code: Shift Solenoid/V B.
• Engine code: P0755 (Shift solenoid B circuit improper voltage).

Other OBD2 Codes + Test Results

• P0755 (Shift solenoid B circuit improper voltage).
• No voltage detected to A or B solenoids during testing.
• TCC solenoid buzzes in park while throttle is opened.

Mechanic Suggestions

• Check grounding of solenoids, as ECM grounds the solenoids rather than sending battery voltage to them.
• Investigate possible ECM problems, as 2002 Sentras are known for ECM issues. There was a recall for removing foam from ECM boxes due to chemical release damaging the ECM. Check for foam presence and damage, even if foam has been removed.

Final Fix

• Cleaned the negative battery terminal on the transmission housing.
• Checked resistance and energized solenoid at the TCM, with readings within expected parameters.
• Cleared all TCM and PCM codes, then monitored TCM inputs and outputs during an extended test drive.
• No recurrence of the code observed after the above steps, suggesting possible resolution of the issue related to the TCM.

Case #2: Ford

Vehicle Information 1997 Ford F-150 XL 4.2L

Issue + Repair History

• Truck neutrals out at stop signs, requires shifting down to 2nd or 1st gear to take off.
• Code P0755 (Shift solenoid B circuit improper voltage).
• Previous repairs: Installed Jasper remanufactured transmission, replaced PCM, replaced range sensor.

Other OBD2 Codes + Test Results

• P0755 (Shift solenoid B circuit improper voltage).

Mechanic Suggestions

• Check for a broken wire on the 2-3 shift solenoid, especially if the wire loom is laying on the exhaust, grounding the solenoid intermittently.
• Investigate the possibility of a sticking 3-4 shift valve or restricted shift solenoid, as this can cause uncontrollable movement in the valve body.
• Check for low fluid level, poor line rise, misadjusted manual linkage, or other issues listed in the diagnostic software.
• Ensure proper power supply from the ECM to the shift solenoids and inspect the wiring harness for any damage or breaks.
• Consider contacting Jasper’s technical department for assistance, especially since a Jasper transmission was installed.

Final Fix

• Found a broken wire on the 2-3 shift solenoid, which was grounding the solenoid intermittently due to being in contact with the exhaust.
• Repositioned the wire loom away from the exhaust to prevent further grounding issues, resolving the neutral out condition and recurrence of code P0755.

Case #3: Chrysler

Vehicle Information 2004 Chrysler Pacifica 3.5L

Issue + Repair History

• Car appears to be in default mode, with 2nd gear starts and illuminated MIL with code P0755 (2-4 solenoid circuit).
• Previous repair attempt: Replaced solenoid pack, but no improvement observed.

Other OBD2 Codes + Test Results

• P0755 (2-4 solenoid circuit).

Mechanic Suggestions

• Verify the integrity of the 2-4 solenoid wire and the build date of the PCM. A Chrysler TSB suggests replacing the NGC controller if the vehicle was built late August or early September of 2003.
• Consider the possibility of a bad internal controller, which may require valve body removal for access.
• Check the integrity of the 2-4 circuit; if okay, proceed with solenoid pack replacement.
• Approach the problem not solely as a transmission issue but also inspect other components like the body module and connectors for wiring integrity.
• Use Mopar-branded solenoid packs as off-brand or remanufactured ones might not be reliable.
• Monitor input and output speed sensors, and inspect pin fit on the solenoid block, speed sensors, and TCM.
• PCM problems are common in these vehicles, even without a specific code, and replacement may be necessary.
• Clean and bend the tabs of the solenoid connector for better contact.
• Use a simulator tool to verify the integrity of solenoid control circuits and consider replacing the NGC controller based on Chrysler’s TSB recommendations.

Final Fix

• Vehicle required a new PCM installed by the dealer, resolving the issue.

Diagnostic Step	Explanation
Check solenoid’s grounding and wiring integrity	Ensure the solenoid is properly grounded to the ECM/PCM.
Inspect the ECM for known issues	Check for recalls or common failures specific to the vehicle model.
Test solenoid operation from the TCM/PCM	Direct testing can confirm if the solenoid is functioning correctly.
Clear codes and monitor with an extended test drive	Helps determine if the issue is resolved or persists.
Inspect the wiring harness	Look for any signs of damage, wear, or grounding issues.

Addressing a P0755 code involves a comprehensive check of the shift solenoid circuit, including the solenoid itself, electrical connections, and control modules. The resolution often requires electrical diagnostics, possibly followed by mechanical repairs or part replacements. Given the complexity of modern transmission systems, professional diagnosis and repair are recommended to ensure a correct and safe resolution to the problem.