P0229
Throttle/Pedal Position Sensor/Switch C Circuit IntermittentP0229 is a generic OBD-II powertrain diagnostic trouble code: Throttle/Pedal Position Sensor/Switch C Circuit Intermittent. It is logged by the engine control unit when the throttle monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0229 means
P0229 is a generic OBD-II code indicating that the PCM has detected an intermittent or erratic signal from the Throttle Position Sensor or Accelerator Pedal Position sensor channel "C" circuit. Unlike P0225 (general malfunction), P0227 (persistently low), or P0228 (persistently high), P0229 describes a signal that drops out, spikes, or fluctuates unpredictably — sometimes within normal range and sometimes outside it — without settling into a continuous failure state. The PCM may log the fault, and the MIL may illuminate, but symptoms can vanish completely after a restart, only to return under vibration, heat, or sustained throttle input.
Intermittent faults of this nature are most commonly caused by mechanical degradation: loose connector pins that momentarily break contact, a wiring harness with a partially broken conductor that only loses continuity under flexing, or an APP sensor with a worn resistive track that produces momentary signal dropouts. Temperature cycling can cause thermal expansion and contraction to open and close marginal connections. Because the fault is not always reproducible on the bench, technicians should replicate driving conditions, apply physical stress to the harness, and monitor live C-channel data to catch the event.
P0229 carries the same safety implications as the continuous TPS-C faults. When the PCM detects the intermittent disagreement, it will engage limp-home mode for the duration of the event, which can manifest as a sudden unexpected loss of power while driving. Symptoms resolving after restart does not mean the underlying fault has cleared — the stored code and the degraded component remain and the failure will recur and likely worsen over time.
Common causes
Most-frequently reported root causes when P0229 is logged.
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1
Loose, corroded, or intermittently contacting connector pin on the C-channel signal, reference, or ground terminal.
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2
Partially broken conductor in the wiring harness that loses continuity under flexing, vibration, or thermal stress.
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3
Worn resistive track inside the TPS or APP sensor producing momentary signal dropouts at specific throttle positions.
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4
Chafed wiring that intermittently shorts to ground or to another circuit under vibration.
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5
Failing PCM with an intermittently faulty C-channel analog input stage (rare).
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6
Thermal expansion causing a marginal solder joint or connector to open at operating temperature and recover when cold.
Symptoms drivers notice
How to diagnose P0229
A typical diagnostic flow when this code is present.
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1
Retrieve all stored codes, freeze frame data, and check for pending codes; verify the fault is specifically on channel C and note the count of fault occurrences if the scan tool tracks them.
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2
With the scan tool graphing C-channel live data, attempt to replicate the fault by performing a full throttle sweep and noting any signal dropout, spike, or sudden voltage discontinuity.
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3
Physically flex and tug the sensor wiring harness at multiple points while monitoring live C-channel voltage to isolate a chafed or broken conductor.
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4
Inspect the sensor connector carefully for corroded, fretting, or loose-fitting pins on the C-channel signal, 5-volt reference, and ground terminals.
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5
Check battery voltage supply to the sensor and verify the 5-volt reference remains stable across the full RPM and load range.
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6
Measure sensor resistance across the C-track at multiple throttle positions for consistency; any sudden jump or open circuit points to internal sensor wear.
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7
After repairing the identified fault, clear codes and perform an extended road test under varying load and temperature conditions to confirm the fault does not recur.
Related powertrain codes
- P0120 — Throttle Position Sensor/Switch A Circuit Malfunction
- P0121 — Throttle Position Sensor/Switch A Circuit Range/Performance Problem
- P0122 — Throttle Position Sensor/Switch A Circuit Low Input
- P0123 — Throttle Position Sensor/Switch A Circuit High Input
- P0124 — Throttle Position Sensor/Switch A Circuit Intermittent
- P0220 — Throttle/Pedal Position Sensor/Switch B Circuit Malfunction
Frequently asked questions
Why do P0229 symptoms disappear after a restart?
Intermittent faults often depend on specific conditions — heat, vibration, or a particular throttle position — to manifest. After a cold restart, thermal contraction may re-establish a marginal connection, or the PCM resets its fault counters. The stored code remains and the underlying fault is still present, ready to recur under the same conditions.
How do I diagnose a fault that is not present during testing?
Replicate the conditions under which the fault occurred: warm the vehicle to full operating temperature, apply physical stress (light tapping and flexing) to the harness sections while monitoring C-channel live data, and use roads with vibration. Some scan tools support a minimum/maximum capture mode that will record the lowest or highest voltage seen, which can reveal a momentary dropout you might otherwise miss.
Is P0229 less serious than P0225, P0227, or P0228?
Not in terms of safety — it carries the same risk of sudden limp-home activation while driving. An intermittent fault is often harder to diagnose but represents an actively degrading component or connection that will eventually become a continuous fault. Prompt diagnosis is recommended.
Could P0229 be caused by a battery or charging system problem?
Yes. Voltage instability from a weak battery or failing alternator can cause the 5-volt sensor reference supply to fluctuate, producing intermittent anomalies on all TPS/APP channels including C. If multiple sensor-related codes appear together, check charging system voltage and battery condition before focusing on the sensor or wiring.
Disabling P0229 in software
RaceTune can permanently disable P0229 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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