Fix P0222: Mechanic’s solutions that WORKED

The P0222 is an OBD-II code indicating that the throttle position sensor “B” circuit has reported a low input. This sensor is key in monitoring the throttle’s position and relaying that data to the ECM, which adjusts engine operations accordingly. A low input from this sensor can cause erratic engine behavior, including poor acceleration and idling.

P0222 quick overview

Meaning	P0222: Throttle/Pedal Position Sensor/Switch “B” Circuit Low Input
Is it serious?	Yes, as it directly impacts engine performance and response.
Possible causes	– Faulty throttle position sensor – Wiring issues in the sensor circuit – Poor electrical connections – PCM issues (less common)
How to diagnose?	Check the throttle position sensor and wiring for damage or disconnections. Verify the sensor’s voltage with the key on and engine off. Inspect the 5-volt reference wire for proper voltage. Monitor TPS signal wires for voltage changes when manually operating the throttle. Use a factory scan tool to command and observe throttle plate movement.

How to fix P0222 – learn from mechanics

I looked into P0222 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: Dodge

Vehicle information 2003 Dodge Ram 2500 5.7L

Issue + repair history

• Throttle plate not moving, no vacuum in the intake
• Replaced throttle assembly and performed relearn, but issue persisted
• Throttle position sensors (TPS) readings in spec with key on engine off (KOEO) but throttle plates still not moving

Other OBD2 Codes + Test Results

• P2106
• P2172
• P2108
• P0222
• P0123

Mechanic suggestions

• Address P2108 first, as it indicates an internal PCM fault or reflash problem; if the code persists, the PCM may need replacement
• Investigate codes P0222 and P0123 related to TPS voltages; ensure the TPS voltages are correctly aligned (low at idle, high at wide-open throttle)
• Check 5-volt reference wire (Orange) at Electronic Throttle Control (ETC) for proper voltage with KOEO
• Monitor TPS signal wires (WT/DG for TPS 1, DB/DG for TPS 2) for voltage changes while manually opening the throttle valve
• Consider checking compression, as broken valve springs can trigger fail-safe mode to prevent further damage; if broken springs are found, replace all springs
• Confirm throttle plate behavior using factory scan tool, as there may be a function to command ETC to function and observe throttle plate movement

Final fix The issue was resolved by discovering a split intake underneath the vehicle, causing the throttle plate to not move. Replacing the intake resolved the problem.

Case #2: Mercedes

Vehicle information 2001 Mercedes-Benz C230, 203, 2.6L

Issue + repair history

• Small accident resulted in a broken front windscreen
• Car experienced no acceleration after the accident, codes retrieved: P0222 (Throttle/pedal position sensor/switch B Circuit low input)
• No data available on this non-American model in iATN database or MOD5/Alldata
• Removed driver’s side carpet to dry out, inspected wiring which appeared good and clean
• Lack of information on repair approach prompted seeking advice

Other OBD2 Codes + Test Results None mentioned

Mechanic suggestions

• Investigate accelerator pedal assembly as it could be faulty, leading to the low input circuit issue
• Check for water intrusion in fuse box or engine ECU due to the broken windscreen, as water entry could cause similar symptoms
• After drying components and connectors thoroughly, reassemble and recheck/reset codes; factory tool may be required for thorough diagnostics and reset

Final fix Replacing the accelerator pedal assembly resolved the issue. Despite initial suspicion related to water entry from the broken windscreen, the actual cause was the faulty pedal assembly

Case #3:

Vehicle information 2004 Mini Cooper, 1.6L

Issue + repair history

• Transmission issues noted when shifting into 5th and 6th gears, behaving as if dropping out or downshifting to lower gear, with RPMs remaining high at about 5000
• Fluid level checked and found full and clean
• ECM scanned, revealing codes P0123 (TPS sensor 1 input high) and P0222 (TPS sensor 2 input high)
• Unable to communicate with TCM using Snap-on scanner or Launch; other modules communicate fine
• Verified power and grounds at TCM, as well as square wave signal on data bus lines
• Unplugging TCM resulted in setting code P1611 (loss of communication with TCM) stored in ECM
• Lights in shifter inoperative when TCM unplugged, unable to engage reverse or forward gears

Other OBD2 Codes + Test Results None mentioned

Mechanic suggestions

• Consider trying a new throttle position sensor (TPS) as a potential solution
• Obtain a schematic or pinout of the TCM to the transmission plug to check signals, powers, and grounds; verify these while a partner manually shifts gears
• Investigate the shifter module for any spills or contaminants, and check TPS voltage at accelerator pedal position (APP) and at throttle body

Final fix Customer took the car to Mini dealership, where the TCM was flashed and a speed sensor was replaced.

Diagnostic Step	Explanation
Check TPS and wiring	Looks for physical damage or disconnection affecting signal strength.
Verify sensor voltage	Ensures the sensor operates within the expected voltage range.
Inspect 5-volt reference	Confirms the ECM provides the correct power to the sensor.
Monitor signal changes	Helps diagnose intermittent issues affecting throttle response.
Command throttle movement	Uses diagnostic tools to directly test the throttle assembly’s functionality.

The service cases of a Dodge Ram, Mercedes-Benz C230, and Mini Cooper illustrate the importance of thorough diagnostics when dealing with P0222. Solutions ranged from replacing the throttle assembly or accelerator pedal assembly to software updates and electrical repairs, highlighting the code’s potential impact on vehicle operation.