What Does It Mean?
This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to vehicles equipped with OBD-II. Although generic, specific repair steps may vary by make/model.
When I encountered a stored P0228 code, I found it means the Powertrain Control Module (PCM) detected a high voltage input from the Throttle Position Sensor (TPS) circuit or a specific Pedal Position Sensor (PPS) circuit. C refers to a particular circuit, sensor, or area of a specific circuit.
Consult a reliable vehicle information source (All Data DIY will work) for details about the vehicle in question. This code is only used in vehicles with Drive-By-Wire (DBW) systems.
The PCM controls the DBW system using a throttle actuator motor, one or more pedal position sensors (sometimes called accelerator pedal position sensors), and multiple throttle position sensors. The sensors are supplied with reference voltage (typically 5 volts) and ground. Most TPS/PPS sensors are potentiometer-type and complete their respective circuits. A pivoting extension, on the accelerator pedal or throttle shaft, operates the sensor contacts. The sensor’s resistance changes as the contacts move across the sensor’s circuit board, causing variations in circuit resistance and signal input voltage to the PCM.
If the signal input voltage exceeds a programmed limit, for an extended period under certain conditions, a P0228 code will be stored and a Malfunction Indicator Lamp (MIL) may illuminate.
Symptoms
/ Severity
When this code is stored, the PCM typically enters limp mode. Engine acceleration will be severely limited (if not disabled) in this mode. Symptoms of a P0228 code may include:
Stuck throttle (at any RPM)
Limited or no acceleration
Engine stalling at idle
Hesitation during acceleration
Inoperative cruise control
Causes
Possible causes of this engine code include:
Open or shorted circuits between TPS, PPS, and PCM
Faulty TPS or PPS
Corroded electrical connectors
Faulty cable actuator motor
Diagnostic and Repair Procedures
A good starting point is always checking Technical Service Bulletins (TSBs) for your specific vehicle. Your issue might be a known problem with a published manufacturer fix, saving time and money during diagnosis.
I would access a diagnostic scanner, digital volt/ohmmeter (DVOM), and vehicle information source like All Data (DIY) to diagnose a P0228 code.
My first diagnostic step would be a visual inspection of all cables and connectors related to the system. I also like checking the throttle plate for signs of carbon buildup or damage. Excessive carbon buildup, keeping the throttle body open at startup, can cause a P0228 code to store. Clean carbon from the throttle body per manufacturer recommendations and repair or replace faulty wiring/components as needed, then retest the DBW system.
Next, I connect the scanner to the vehicle’s diagnostic port and retrieve all stored trouble codes. I note them in case I need the order codes were stored. I also like saving all related freeze frame data. These notes can prove helpful if P0228 proves intermittent. Now I clear the codes and test drive the vehicle. If the code resets, I continue my diagnosis.
Voltage spikes and inconsistencies between TPS, PPS, and PCM can be detected using scanner data stream. Narrow the data stream to display only relevant data for faster response. If no spikes/inconsistencies are detected, use the DVOM to retrieve live data from each sensor individually. To get live data with DVOM, connect test leads to appropriate signal and ground circuits and observe DVOM display while operating DBW. Look for voltage spikes when throttle is slowly operated from closed to wide-open position. Voltage typically ranges from 0.5 volts at closed throttle to 4.5 volts at wide-open throttle. If spikes or other irregularities are detected, suspect the tested sensor is faulty. An oscilloscope is also an excellent tool for testing sensor operation.
Additional Diagnostic Notes:
Some manufacturers require throttle body, throttle actuator motor, and all throttle position sensors be replaced together