By iCarsoft Official Store Technical Team, Automotive Diagnostics Editors · Updated September 11, 2026 · OEM technical references checked
Quick Answer
The P0338 code identifies a crankshaft position sensor A circuit-high fault. It does not prove a bad sensor or excessive engine speed. Some OEM implementations monitor pulse-pattern errors rather than a simple high-voltage condition. Save the complete scan and identify the exact monitor before choosing circuit or mechanical tests.
What Does the P0338 Code Mean?
The P0338 code means Crankshaft Position Sensor A Circuit High Input. It names a monitored result, not a guaranteed failed part. The reporting module, suffix and companion faults determine the relevant test branch.
The crankshaft sensor supplies position and speed information for engine control. Powered electronic sensors and inductive pickups have different signal shapes and test connections. Locate sensor A from the engine diagram; A does not automatically identify a bank, connector position or vehicle side.
Scan-tool RPM is the controller’s interpretation, not proof of clean pulses. A missing RPM display can also reflect data availability or communications. Compare the scan with the correct physical measurement before condemning hardware.
GM's 2008 LNF engine OBD certification document lists P0338 as a rationality check involving the number of teeth counted between reference-gap events. This is a scoped monitor example, not a universal voltage limit. It explains why a diagnosis based only on the word high can miss a distorted signal or reference-pattern problem.
The archived 2007 Cadillac CTS 3.6L procedure calls P0338 a high-duty-cycle fault and includes reluctor inspection. Confirm current VIN service information. Do not combine its sensor location, tooth counts or procedure with the separate LNF example.
Separate P0338 from adjacent fault families
| Code | General description | Key distinction |
|---|---|---|
| P0335 | Crankshaft position sensor A circuit | A general circuit fault; use its own OEM test tree. |
| P0336 | Crankshaft position sensor A range/performance | Not interchangeable with P0338 merely because both can involve waveform quality. |
| P0337 | Crankshaft position sensor A circuit low | Low classification has a separate monitor and fault path. |
| P0338 | Crankshaft position sensor A circuit high | Check whether this application evaluates voltage, duty cycle or pulse rationality. |
| P0339 | Crankshaft position sensor A intermittent | An intermittent record is distinct from the circuit-high classification. |
Record the complete P0338 description. The suffix, reporting module and companion faults can change the diagnostic path. Use the manufacturer's full wording and test procedure for the exact vehicle.
P0338 Symptoms and Likely Causes
P0338 symptoms depend on fault status and the fallback strategy. Record what the driver and modules reported. A symptom list is not a parts list.
Record whether the engine turns normally and whether the controller reports engine speed. A no-start condition still needs a complete diagnosis.
Note whether the event followed heat soak, vibration or recent work. Stop driving if repeated stalling makes operation unsafe.
Misfire and synchronization complaints can accompany a signal problem. Save companion faults rather than treating every symptom as a sensor failure.
An intermittent event may have passed before inspection. Preserve the failure conditions and avoid calling the repair successful after one clean start.
Practical cause-checking order
- Connector and routing: Inspect terminal fit, contamination, oil or water entry and harness contact with moving or hot components. A connector that looks seated may still contain a backed-out terminal. Use the approved terminal inspection method rather than widening a terminal with a probe.
- Sensor circuit: A signal path, low reference or applicable sensor supply can be affected by an open, short or excessive resistance. Determine the actual sensor design first. A two-wire inductive sensor should not be tested as though it has the same supply circuit as a powered sensor.
- Signal and reference pattern: An incorrect waveform can reflect a sensor problem, damaged reference features, mounting error or interference. Distinguish electrical noise from a repeatable pattern defect. Scope settings and engine speed influence the captured waveform, so compare under the specified conditions.
- Recent installation: Check recent sensor, crankshaft, timing, engine or harness work. Verify part identity and specified installation requirements. Do not infer incorrect mechanical timing merely from a circuit-high code.
- Controller evidence: Consider controller or calibration faults only after applicable external tests pass. Confirm supply, grounds, signal arrival and service information. Module replacement may require programming and setup.
Did P0338 appear after recent sensor, engine, timing or wiring work? Recheck the documented connections, parts and setup steps affected by that work. Record battery and software history; a post-repair code does not prove the new part is defective.
How Serious Is P0338, and Can You Drive?
Do not drive a vehicle that stalls unpredictably or loses power in traffic. Arrange transport if starting or running is unreliable. If operation remains normal, follow the owner's manual and arrange prompt diagnosis; P0338 alone cannot establish a safe distance or guarantee the next restart.
Record temperature, load, speed, start state and recent service. Do not reproduce a severe symptom on public roads; another warning can make the situation more urgent.
Stop and arrange a tow if the engine stalls repeatedly, acceleration becomes unsafe, a flashing warning accompanies severe misfire, or new mechanical noise, smoke or an oil-pressure warning appears.
Secure the vehicle before cranking tests. Keep probes, leads, clothing and hands away from belts, pulleys and automatic fans. Use ventilation for running tests and the required support for access underneath. Do not hold loose test leads near rotating parts or bypass starting safeguards.
How to Diagnose P0338 in the Right Order
-
Save the starting and failure record
Save P0338 status, full description, available freeze frame and companion codes before clearing. Record whether the problem occurs while cranking, running or restarting hot. Include battery-service and replacement-part history so the next test investigates the original event.
-
Identify the sensor and OEM monitor
Match the VIN and engine to the current diagram and fault procedure. Establish whether the sensor is powered or inductive and what high means for this monitor. Identify approved test points and the reference-wheel design; never copy terminal numbers or test limits from another engine.
-
Inspect the undisturbed signal path
With the engine stopped and access made safe, inspect connectors, harness protection, mounting and disturbed service areas. Look for rubbing, heat damage and loose retention without pulling on wires. Record findings before disconnecting anything. If the OEM procedure calls for reference-wheel inspection, use its access method; do not dismantle timing components merely because an online code list mentions them.
-
Measure the correct circuit safely
Use the specified meter or oscilloscope connections for this sensor architecture. Test applicable supply and low-reference paths, then compare the signal at approved points when required. A continuity reading alone may miss a loaded or intermittent fault. Avoid grounding an unknown circuit with a scope lead, piercing insulation unnecessarily or applying external voltage to a controller input.
-
Compare waveform and controller evidence
Record a waveform under the permitted operating condition and compare it with the matching reference. Review available RPM and synchronization data alongside the capture. A steady meter average can hide missing or extra pulses. Use changes along the signal path to distinguish wiring from source-pattern evidence; a scanner display alone cannot establish reluctor condition or electrical signal integrity.
-
Confirm the repair and required setup
Repair only the demonstrated fault and restore routing, seals and fasteners. Check whether the specific repair requires a crankshaft variation learn or another setup, and confirm prerequisites before running it. Reproduce the applicable verification safely, save the result and review current or pending codes. Do not use a relearn to conceal an unresolved waveform or circuit problem.
Specifications are vehicle-specific. Use the exact VIN specifications, approved test points and required operating state. No generic value or drive cycle can replace the applicable procedure. Manufacturer examples here do not establish specifications for other applications.
P0338 Repairs and Typical Costs
The correct P0338 repair follows the failed test. Wiring, a physical repair, a proven component, software and controller work are different outcomes. Do not replace an assembly from the generic code alone.
Recheck installation and required setup after repair. If the fault began after sensor or engine work, confirm the exact replacement part, connector engagement, routing, mounting and applicable setup. A compatible plug is not proof of a compatible sensor. A damaged or incorrect reference wheel will not be repaired by repeatedly installing sensors or clearing memory.
| Possible path | Current US estimate |
|---|---|
| Diagnose connector fit, harness damage and intermittent signal loss | VIN-specific quote |
| Repair the proven supply, reference or signal circuit | VIN-specific quote |
| Replace a sensor only after the applicable component test fails | VIN-specific quote |
| Correct a demonstrated mounting or reluctor problem | VIN-specific quote |
| Perform required setup or justified controller work | VIN-specific quote |
These are alternative repair paths, not prices to add together. Request a VIN-specific quote separating diagnosis, parts, labor, fluids, taxes, required setup and verification. Ask which failed test supports the proposed repair and whether warranty coverage applies.
Using iCarsoft CR MAX BT for P0338
On a supported vehicle, iCarsoft CR MAX BT can retrieve accessible module faults, save available freeze frame, display ECU-provided live data and create a diagnostic report. For P0338, preserve the original evidence and compare related modules before clearing an erasable record.
Preserve the crankshaft position signal evidence
iCarsoft CR MAX BT
Review supported codes and relevant live data together. Confirm the exact VIN, controller access, PIDs and any requested active test with iCarsoft before purchase; generic product capabilities do not guarantee a P0338-specific function.
Check current CR MAX BT price and availabilityCheck CR MAX BT compatibility by VINThe official product page describes wireless all-system diagnostics and supported bidirectional controls; available live data, test coverage and coding functions vary with the vehicle, ECU and software. Confirm the requested function by VIN before purchase. Follow OEM prerequisites and stop for abnormal operation.
Know the measurement boundary. Scan data describes ECU-provided information; it does not directly prove the physical condition of the crankshaft position signal. Use the specified oscilloscope, correctly connected meter, wiring diagram and approved physical inspection where required, and compare reported values with the relevant measured evidence.
Verify the P0338 Repair
After repair, verify connectors, harness clearance, setup and controller supply. Save post-repair findings, then clear only erasable records through the approved procedure. Battery disconnection is not a repair.
Run the manufacturer's applicable verification conditions in a safe workshop or route. Compare the original operating state with current data for the crankshaft position signal, and check current and pending faults in related modules. One clean start or idle period does not prove that every conditional monitor has completed.
If P0338 returns, compare its suffix, status, failure order and operating conditions with the saved baseline before replacing another part. Revisit the failed branch and inspect anything disturbed. Keep mechanical repair, monitor completion, readiness and local inspection eligibility as separate outcomes.
A permanent P0338 can remain immediately after a successful repair. If stored as a permanent DTC, it cannot be erased by a scan tool or battery disconnect. The vehicle must complete the applicable successful monitor verification.
Related Crankshaft Position Signal Code Guides
P0338 Frequently Asked Questions
Does P0338 always mean the sensor voltage is too high?
No. Circuit high is the general code label, but the OEM implementation matters. The cited GM LNF example evaluates reference-pattern rationality, and the archived CTS procedure uses high-duty-cycle wording. Identify the actual monitor before using voltage, waveform or mechanical tests.
What should I check first for P0338?
Save every module's codes and freeze frame before clearing. Confirm the full definition, suffix and VIN architecture. Then inspect recent sensor, engine, timing or wiring work, connectors and shared supplies. Those facts determine whether the next test needs the specified oscilloscope, correctly connected meter, wiring diagram and approved physical inspection or a manufacturer-specific functional procedure.
Can I drive with the P0338 code?
Do not drive a vehicle that stalls unpredictably or loses power in traffic. Arrange transport if starting or running is unreliable. If operation remains normal, follow the owner's manual and arrange prompt diagnosis; P0338 alone cannot establish a safe distance or guarantee the next restart.
Why did P0338 return after a part was replaced?
A replacement can leave the original harness fault, incorrect part or distorted reference pattern unchanged. A required setup procedure may also remain incomplete. Compare the returning fault's status and operating conditions with the original record, then test the unresolved branch instead of assuming another sensor is needed.
What should a P0338 repair estimate include?
Ask for the failed-test evidence and a VIN-specific breakdown of diagnosis, parts, labor, taxes, required setup and verification. A code alone cannot establish the repair price.
Can CR MAX BT diagnose and clear P0338?
On a supported vehicle, CR MAX BT can organize available faults, freeze frame, live data and reports, and can clear erasable records after repair. Confirm exact ECU coverage. It cannot force-clear a permanent DTC or replace physical measurements for the crankshaft position signal.
The iCarsoft Official Store Technical Team maintains the store's fault-code library. This guide organizes published manufacturer evidence and verified product information; it does not document a hands-on test of a particular vehicle or claim an individual engineer's review.
Technical and cost references
- GM 2008 LNF Engine OBD Certification Documentation. P0338 reference-gap tooth-count rationality example, page 13; application-specific monitor data, not universal test values.
- 2007 Cadillac CTS 3.6L P0338 manufacturer service procedure, archived by Operation CHARM. Historical OEM procedure reproduced by a third-party archive; confirm current service information before applying its high-duty-cycle diagnostic branch.
- California Bureau of Automotive Repair — On-Board Diagnostic Test Reference. Permanent DTCs are removed by the vehicle after applicable verification, not by a scan-tool erase command.
Product information: Official iCarsoft CR MAX BT page.
Editorial note: General diagnostic education, not a substitute for the owner's manual, current VIN-specific service information or professional inspection. Test limits, procedures, coverage and costs vary. Related articles provide context; apply only the specifications and repair procedures that match the vehicle. No universal failure rate, repair price or outcome is implied.
