Everything tests fine. Does that mean the code is wrong?

No — it means the fault was not present while you were measuring, which is what intermittent describes. Static tests on this code have almost no diagnostic value: a spread terminal, a wire worn to a few strands, or corrosion that only fails when damp will all read perfectly at rest. The tests that count are the ones performed while the circuit is disturbed — graphing the channel live while flexing the harness and working the connector, and sweeping the pedal slowly through its full range looking for a momentary dropout at one specific angle. If it still will not appear, log data over a real drive in the conditions the owner describes.

Is it more likely the 'C' sensor or the wiring?

The wiring, and the reason is structural. The redundant position channels are built into the same assembly and routed through the same connector on the same harness, so anything mechanical — a spread terminal, a chafe point, moisture in a plug — disturbs whichever wires are nearby without regard to which channel they belong to. A failed 'C' sensor element is a much rarer event than a shared connection problem that happened to catch the 'C' pin. Check code history: if other channels have also glitched, the connector is your answer. Only a channel that fails repeatedly and alone, with the others clean across many cycles, makes the sensor element the leading suspect.

Could the battery really cause a throttle position code?

Yes, and it is worth ruling out early because it is quick. The position sensors report against a regulated reference derived from system voltage. A weak battery, an alternator with a failing diode, or excessive ripple voltage moves that reference around, and when the channels are compared against each other the module can see an implausibility that exists in the reference rather than in the sensors. Nothing in the throttle system is faulty in that case, and replacing sensors will not help. A ripple measurement takes a minute and occasionally ends the diagnosis on the spot.

How urgent is this if it only happens occasionally?

More urgent than the frequency suggests. Each of those momentary events is the module entering a fail-safe state because it briefly could not trust a throttle demand signal, and the fail-safe response is a power reduction that arrives with no warning to the driver. Occasional today does not stay occasional — the mechanical causes behind an intermittent, a spreading terminal or a wire down to its last strands, get worse rather than better. It is safe enough to drive to a shop, but this is not a code to leave for months, particularly if the vehicle is used for overtaking or merging on fast roads.

OBD-II trouble code

P0229: Throttle/Pedal Position Sensor/Switch 'C' Circuit Intermittent

The third throttle or pedal position channel is glitching rather than failing. This is the least common code in a block that is already uncommon, and that rarity is itself diagnostically useful: it usually means the fault is in wiring shared with the other channels rather than in the 'C' sensor.

Medium severityPowertrainThrottle / IdleDrivable short-term

Quick facts

System: Powertrain
Category: Throttle / Idle
Severity: Medium severity
Drivable: Usually safe to drive short-term
Repair cost range: $100 – $700
DIY difficulty: Intermediate DIY

What does P0229 mean?

Electronic throttle control is built on redundancy. Several position channels — commonly two at the accelerator pedal and two inside the throttle body — report the same physical movement, and the module cross-checks them before it will act on any throttle request. The letters identify the channels, and 'C' is the third. P0229 is the intermittent fault for that channel: the module caught the signal misbehaving briefly and then returning to a valid state, without any hard low or high condition lasting long enough to qualify as its own code.

Two separate things make this code awkward, and it is worth naming both before reaching for a meter.

The first is that intermittent means the fault is not there when you look. Every static measurement will pass. The circuit will read correctly at rest, the sensor will sweep smoothly, resistance will be in specification, and none of that is evidence the circuit is healthy — it only shows the fault was absent during the measurement. The only tests that carry weight are dynamic ones: graphing the channel live while flexing the harness, working the connector, running the wiring through its full range of movement, and sweeping the pedal or throttle plate slowly across its whole travel while watching for a discontinuity. A worn spot on a resistive track will show up as a momentary drop at one specific angle and will be invisible to any reading taken at rest.

The second is more interesting, and it is specific to this code being a 'C' channel intermittent. Three-and-four-channel systems put the redundant sensors in the same physical assembly and route them through the same connector on the same harness. If a connector terminal is spread, if the harness has chafed, or if moisture has got into a plug, the mechanical cause does not respect channel boundaries — it disturbs whatever wires happen to be nearby. That means a genuine 'C' sensor element fault, which would be a rare event on a rarely-used channel, is a much less likely explanation than a shared mechanical problem that happened to catch the 'C' pin. The practical consequence: check whether any other throttle or pedal position code has ever been stored, including in history and pending memory, and check whether the module logged more than one channel glitching in the same drive cycle. Multiple channels implicated points squarely at the connector or the harness. A single channel implicated repeatedly, with the others clean across many cycles, is what would make you suspect the sensor element itself — and that is the less common outcome.

Before either line of inquiry, confirm in service data which physical sensor your manufacturer designates 'C'. Letter assignment is not standardised across platforms, and on a code from this block, ordering a part for the wrong sensor is the most expensive mistake available.

Charging system health deserves its own check. The position sensors work against a regulated reference derived from system voltage, and a weak battery, a failing alternator, or excessive alternator ripple shifts that reference in ways that produce intermittent implausibility on hardware with nothing wrong with it. Measuring ripple takes a minute and it occasionally ends the whole diagnosis.

What the driver reports matches the electrical picture. Not a permanent limp mode, but momentary events: a brief hesitation, an unexpected dip in power that recovers on its own, a flicker of the reduced-power warning, a check engine light that appears and later disappears. Those are real fail-safe entries, brief because the module returned control as soon as the channels agreed again. They deserve to be taken seriously — a channel that drops out for a fraction of a second in traffic today can drop out at a worse moment, and the fail-safe response is a power reduction that arrives without warning.

Common causes

Spread, loose, or backed-out terminal in the connector shared by the redundant position channels
Connector not fully seated, or a broken locking tab allowing movement under vibration
Chafed harness worn to a few strands, opening under flex or thermal expansion
Moisture or corrosion inside a connector that conducts when dry and fails when damp
Wear spot on the 'C' sensor's resistive track that glitches at one particular angle of travel
Weak battery, failing alternator, or excessive ripple voltage shifting the sensor reference
Poor sensor ground with intermittent high resistance under load
Connector disturbed during unrelated work and never fully re-seated
Marginal internal connection inside the pedal or throttle body assembly

Symptoms

Momentary hesitation or a brief dip in power that recovers by itself
Reduced-power warning flickering on and off
Check engine light appearing and later clearing without intervention
Cruise control dropping out briefly
Fault absent during testing while the owner's description is consistent and specific
Symptoms correlating with rough road surfaces, cold mornings, or wet weather
Brief unexplained surge on light throttle
Pending codes present with no current fault stored

Diagnostic steps

1.Confirm in service data which physical sensor this manufacturer calls 'C' before ordering any part. The letter assignment varies between platforms and this block is where wrong parts get bought.
2.Pull code history and pending codes, not just current codes. Whether other channels have also glitched is the single most valuable piece of evidence available on this code.
3.If more than one channel has been implicated in the same drive cycle, treat the shared connector and harness as the fault and stop looking at the 'C' sensor. The redundant channels share a plug, so a mechanical cause does not respect channel boundaries.
4.Test the charging system, including alternator ripple. A shifting reference voltage generates intermittent implausibility on entirely healthy sensors.
5.Graph the 'C' channel live while flexing and tugging the harness section by section and while wiggling the connector. Static readings prove nothing on an intermittent fault.
6.Sweep the pedal and the throttle plate slowly through full travel while graphing, looking for a momentary discontinuity at one specific angle. A worn track spot is invisible to any measurement taken at rest.
7.Inspect the connector terminals for spread, retraction and corrosion, and check the seal and locking tab. Compare terminal tension against an unused cavity if one is available.
8.Perform a loaded voltage-drop test on the sensor ground rather than an unloaded resistance check, since a ground can measure well and still collapse under current.
9.Try to reproduce the condition the owner describes — cold, wet, or rough road — rather than testing only in a warm dry bay, and log data over a real drive if the fault will not appear.

Repair cost

$100 – $700

Diagnosis is the larger share of the bill on this code, because finding an intermittent fault takes time and the fault is usually a connection rather than a part — expect one to two hours of testing, roughly $100 to $300, and that is money better spent than on a speculative sensor. A terminal or connector repair is $80 to $250. An accelerator pedal position sensor assembly is typically $150 to $450 fitted; a throttle body with integrated sensors runs $300 to $700 and usually needs a relearn afterwards. Replacing hardware before the shared-connector question has been answered is the common way to spend the top of this range and still have the fault.

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DIY vs shop

This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.