Fix P0750: Mechanic’s solutions that WORKED

The OBD2 code P0750 indicates an issue with the “Shift Solenoid A” electrical circuit in the transmission. This solenoid is responsible for controlling the flow of hydraulic fluid to engage or disengage different gears, particularly the low and reverse gears. When this code is set, it suggests a malfunction within the solenoid’s control circuit, which can lead to noticeable driving issues such as the vehicle going into limp mode, where it locks into a single gear to prevent further damage.

P0750 quick overview

Meaning	P0750: Low and Reverse Solenoid Circuit Issue (Solenoid A)
Is it serious?	Yes, as it can lead to transmission shifting issues, potentially causing the vehicle to enter limp mode and restrict driving functionality.
Possible causes	– Faulty shift solenoid – Open or short in the solenoid circuit – Poor electrical connection – Malfunctioning Powertrain Control Module (PCM)
How to diagnose?	Check electrical connections and wiring to the solenoid for damage or corrosion. Test the solenoid’s resistance and operation to ensure it falls within specifications. Inspect the PCM’s connections for water intrusion or damage. Swap control wires at the PCM, if possible, to diagnose wire integrity. Perform a solenoid pack self-test using a diagnostic scanner to observe amp draw and pattern.

How to fix P0750 – learn from mechanics

I looked into P0750 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: Ram

Vehicle information

• Vehicle make, model, year: 2012 Ram 1500 Sport 5.7L

Issue + repair history

• OBD2 trouble codes:
  • P0750 – Low and reverse solenoid circuit issue
  • P0562 – Battery voltage low
• Vehicle in fail-safe mode.
• Ohmed the solenoid from PCM connector through the solenoid and back to connector; within specs.
• Code P0562 attributed to a failing battery, replaced with a new one.
• Cleared codes; P0750 immediately returned on startup.
• Monitored voltage to solenoid, found voltage loss on startup due to TPM module losing transmission control voltage signal from PCM.
• Remotely supplied voltage to TPM on trans control wire from PCM; voltage to solenoid restored but code P0750 still reset.
• Load tested solenoid; illuminated light and intact fuse.
• Suspected PCM failure due to logical deduction.

Other OBD2 Codes + Test Results

• OBD2 codes:
  • P0750 – Low and reverse solenoid circuit issue
  • P0562 – Battery voltage low

Mechanic suggestions

• Consider replacing the solenoid pack, which is often the fault for code P0750.
• Perform a self-test of the solenoid with a scope to observe amp draw and pattern.
• Swap L/R control wire and 2C control wire at the PCM to determine if the issue persists.
• Try plugging in a known good solenoid body without pulling the pan to see if the code disappears.
• Inspect PCM connector pins closely for water intrusion and corrosion.

Final fix

• Replaced the PCM, resolving the issue.
• Vehicle has been operating without issues for several weeks.

Case #2: Dodge

Vehicle information

• Vehicle make, model, year: 1999 Dodge Avenger 2.5L

Issue + repair history

• OBD2 trouble codes:
  • P0750 – Limp mode issue
  • P0700 – Transaxle control system malfunction
• Replaced input and output speed sensors.
• Replaced solenoid pack.
• Replaced transmission fluid and filter.
• Checked EATX relay and circuit.

Other OBD2 Codes + Test Results

• OBD2 codes:
  • P0750 – Limp mode issue
  • P0700 –

Mechanic suggestions

• Check power at the solenoid pack; ensure no open circuits.
• Inspect connectors at the solenoid; resize if necessary.
• Load test the wire from the transmission with an automotive bulb to ensure proper continuity.
• Tighten pins for wiring associated with the transmission control module (TCM) and solenoid pack.
• Replace the TCM if found faulty; beware of common issues with remanufactured TCMs.
• Verify power at the transmission; ensure failsafe mode is not causing the absence of power.
• Check wiring from the computer to the solenoid block; replace TCM if necessary.
• Use a fused jumper wire to test power at the TCM connector; compare amp readings for solenoids to diagnose TCM or solenoid pack issues.
• Monitor data such as input and output speeds; inspect for corroded or broken wires.

Final fix

• Replaced the transmission assembly, resolving the issue.
• Vehicle has been driving well since the replacement.

Case #3: Ford

Vehicle information

• Vehicle make, model, year: 2003 Ford Focus SE 2.0L
• Location: Jacksonville, Florida

Issue + repair history

• No 3-4 shift, no engine braking in 1st gear.
• No repair history as it is a new car.
• Electronics test good.

Other OBD2 Codes + Test Results

• OBD2 codes:
  • P0750 – Shift solenoid A malfunction.
• Solenoids were working correctly, but code P0750 was set.

Mechanic suggestions

• Check for an open circuit in shift solenoid A (SSA) circuit, as indicated by code P0750.
• Investigate the possibility of a bad connection causing the issue.
• Consider a potential mechanical problem such as a broken #1 sprag or one-way clutch, especially if no braking occurs in manual 1st gear.
• Shift solenoid A may be causing both problems, as it is active in 4th gear and manual low.
• Perform an air check on solenoid B, located next to solenoid A, to identify any potential issues.

Final fix

• Replaced shift solenoid A, resolving the issue.
• Test drove the vehicle and confirmed proper operation.