P0338 — Crankshaft Position Sensor « A » Circuit High

The diagnostic trouble code P0338 refers to an issue with the crankshaft position sensor circuit, specifically indicating a high voltage signal. This sensor is vital for the engine control unit (ECU) to determine the position of the crankshaft, which is essential for proper fuel injection and ignition timing.

Note that label variations may differ between vehicle manufacturers, but the underlying issue remains similar across most makes and models.

Fast Facts

System affected: Powertrain / Engine management system
Severity: Moderate — can lead to driveability issues but often not immediately dangerous
Main symptoms: Engine stalls, no-start condition, rough running, poor acceleration
Driveability: Limited — vehicle may start but troubleshooting is recommended

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Manufacturer variations for trouble code P0338

Vehicle manufacturers sometimes assign different labels or code formats for similar issues. For P0338, known variations include:

Ford: P0338 – « Crankshaft Position Sensor « A » Circuit High »
Volkswagen / Audi: 00535 / P0338 – « Crankshaft Sensor Circuit High »
BMW: 13xxxx series, often related to crankshaft sensor circuits with similar descriptions
Honda / Acura: Usually expressed as P0338, with wiring or sensor-related descriptions
Other OEMs: Variations around the same theme, with different numeric or alphanumeric labels

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What does trouble code P0338 mean?

P0338 indicates that the ECU has detected a high voltage signal on the crankshaft position sensor « A » circuit. This sensor’s role is to monitor the position and rotational speed of the crankshaft, providing critical data to the ECU to control ignition timing and fuel injection.

The ECU continuously checks the sensor’s voltage and frequency signals. When it perceives an abnormally high voltage — higher than the specified limits — it triggers the P0338 code. This situation can happen due to various issues, often related to wiring or sensor faults.

This code might appear during driving, at startup, or during stringent diagnostic testing, especially if the sensor’s signal becomes erratic or exceeds normal voltage ranges.

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Severity and risks of trouble code P0338

The P0338 code primarily signifies a potential issue with the sensor’s voltage signal, which directly affects the ECU’s ability to accurately determine crankshaft position. This can lead to problems such as poor engine performance, misfires, or difficulty in starting the vehicle. If ignored, it might result in engine stalls or inability to drive the vehicle.

While some vehicles may continue to run with this code, a faulty sensor signal can compromise engine timing, increasing the risk of further damage if not addressed. Therefore, the vehicle should be inspected and repaired promptly.

In terms of driving safety, the vehicle is generally considered Limited—possible driveability issues but not immediately unsafe. However, if symptoms worsen, it can become more difficult to operate safely.

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Symptoms of trouble code P0338

Identifying symptoms associated with P0338 can help target the repair process. Common signs include:

Engine misfires — rough idling or hesitation during acceleration
Difficulty starting the engine or no-start conditions
Engine stalls unexpectedly during driving
Poor engine performance — loss of power or sluggish acceleration
Check Engine Light (MIL) illuminated on the dashboard
Unusual noise or vibration associated with irregular engine timing

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Most likely causes of trouble code P0338

While diagnosing P0338, several potential causes need to be considered. The following are the most common causes, ranked from most to less probable:

Wiring problems: Damaged, frayed, or corroded wiring or connectors that connect the crankshaft sensor to the ECU often cause faulty signals, including high voltage readings.
Faulty crankshaft position sensor: A defective sensor can generate abnormal voltage signals, including signals that are too high.
Sensor circuit short or open: An electrical short or an open circuit in the sensor wiring can lead to abnormal voltage readings.
Bad ECU or software glitch: Although less common, an improperly functioning ECU or software issues might misinterpret signals, causing false high voltage detections.
Problems with the engine’s ground connections: Poor grounding can lead to erroneous signals and voltage issues.

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How to diagnose trouble code P0338

Diagnosing the P0338 code involves a step-by-step process to confirm the fault and identify its root cause. Here are the typical procedures:

Visual inspection: Check the wiring harness leading to and from the crankshaft position sensor for damage, corrosion, or disconnection.
Inspect electrical connectors: Ensure connectors are properly seated, free of dirt, and corrosion. Repair or replace any damaged connections.
Use a scan tool to monitor sensor live data: Observe the voltage signals from the crankshaft sensor during engine operation. Look for abnormal high voltage readings or inconsistent signals.
Check wiring continuity: Perform resistance checks on wiring harnesses to ensure no opens or shorts exist.
Test the sensor: If possible, substitute with a known-good sensor or test the existing sensor per manufacturer specifications.
Ensure proper grounding: Verify that engine grounds are secure and functioning correctly.
Inspect ECU fault codes: Confirm that no other related codes are present that might impact signal integrity.

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Possible repairs for trouble code P0338

Repair strategies depend on the identified cause, but they generally involve mechanical or electrical corrections. The following are potential repairs, ranked by complexity:

Repair or replace damaged wiring or connectors: Basic repair that should be performed by a technician familiar with automotive electrical systems.
Replace the crankshaft position sensor: Usually a straightforward repair, usually a professional task due to sensor accessibility.
Address grounding issues: Ensure all engine grounds are securely attached and free from corrosion.
Update or reprogram ECU software: In rare cases, a software update from the OEM may be required, best performed by a dealership or qualified professional.
Replace ECU (if proven to be faulty): A more complex repair, generally conducted by specialists or authorised service centres.

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Vehicles commonly associated with trouble code P0338 in Europe

The P0338 trouble code tends to appear across various makes and models, particularly those with electrical or sensor-related issues. Some of the common brands and engine families affected include:

Volkswagen Group: Commonly with petrol and diesel engines, including models from VW, Audi, Skoda, and SEAT.

Ford: Widely reported in European Ford models with various EcoBoost and Duratec engines.

BMW: Likely in models with N-series engines and other petrol engines where crankshaft sensors are integrated.

Honda / Acura: Noted in certain models with sensitive sensor circuits.

While this list is not exhaustive, these brands and engine families are frequently associated with this fault in Europe.

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Frequent mistakes with trouble code P0338

Diagnosing and repairing P0338 often encounters common pitfalls that can delay or complicate repair. Recognising and avoiding these mistakes improves diagnosis efficiency:

Ignoring wiring issues: Overlooking wiring harness damage or corrosion is a common mistake, leading to misdiagnosis.
Replacing the sensor without proper testing: Changing the sensor prematurely without confirming circuit faults may be unnecessary and costly.
Not performing live data analysis: Failing to view real-time sensor signals can result in missing the actual problem.
Assuming ECU failure: Jumping straight to ECU replacement rather than inspecting wiring or sensors first.
Neglecting grounding and electrical system health: Overlooking simple grounding issues can cause persistent faults and false readings.

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Quick FAQ — trouble code P0338

Can this code disappear on its own?

It is unlikely that P0338 will resolve itself without intervention, especially if the cause is wiring damage or a faulty sensor. However, temporary glitches or electrical interference might clear temporarily but should be diagnosed further.

Can I keep driving?

While some vehicles may continue to operate, driving with this fault is not recommended long-term. It can lead to poor engine performance or further damage. If the engine stalls or shows severe symptoms, seek professional assistance immediately.

Why does the code return after clearing?

The persistent nature of this fault is usually due to a hardware issue, such as damaged wiring or a faulty sensor, which will cause the code to reappear once the ECU runs its diagnostic checks again.