Number P0340: Camshaft Position Sensor A Circuit Bank 1 or Single Sensor
The camshaft position sensor, almost always a Hall sensor, tells the engine module which stroke cylinder 1 is in – one crank revolution alone is ambiguous – and measures the actual cam phase with variable timing. Sensor A is the intake camshaft, bank 1 the side with cylinder 1. P0340 means no or too
Can you drive with P0340?
Severity: Fix promptly — drivability fault. Short trips at moderate speed only. If the car has entered limp mode (won't rev, stuck in one gear), have it towed rather than forcing it.
If you ignore it: Limp-mode faults tend to strand you, and several of them (misfires, throttle faults) damage other parts while you wait.
This is the #37 most common code in our top-150 library, in the engine position & speed sensors family (Powertrain system). Severity is Number Nest's editorial triage — if the light is flashing or the car feels unsafe, stop driving it whatever any page says.
What P0340 means
The camshaft position sensor, almost always a Hall sensor, tells the engine module which stroke cylinder 1 is in – one crank revolution alone is ambiguous – and measures the actual cam phase with variable timing. Sensor A is the intake camshaft, bank 1 the side with cylinder 1. P0340 means no or too few cam pulses arrive while the crankshaft turns in sync. GM sets it after 5.5 s (or 4 s) of cranking without a cam pulse or fewer than 4 pulses in 3 s running, petrol engines after two trips. Ford checks the ratio of cam to crank events from 200 rpm. The engine usually keeps running but starts longer and loses power as cam timing is held. Bulletins: corroded connectors on GM V8s (PIP5335C), moisture in the oil on short trips in Ford hybrids (SSM 48598).
Systems involved: camshaft position sensor, camshaft tone wheel, sensor wiring, engine control module (ECM/PCM), timing chain.
Causes, ranked by likelihood
| # | Cause | Likelihood |
|---|---|---|
| 1 | Camshaft position sensor faulty (heat, moisture) | most likely |
| 2 | Connector or wiring corroded or open, 5 V reference disturbed | most likely |
| 3 | Tone wheel on the camshaft or phaser damaged, loose or at the wrong distance | possible |
| 4 | Timing drive jumped or wrongly assembled | possible |
| 5 | Moisture in the engine oil from short trips (Ford hybrids) | less common |
Check them in order — the list is ranked so the likely, cheaper causes come before the expensive part.
Symptoms you may notice
- Check engine light on
- Longer cranking before the engine starts
- Loss of power (cam timing held in its base position)
- Rough idle, occasionally stalling
Misdiagnosis traps
- A cam sensor replaced for a stretched timing chain — the sensor reports the timing faithfully; correlation codes (P0016) alongside point mechanical.
- Intermittent harness chafe near the sensor connector causes stalls that never happen on the lift.
How a good shop confirms it
- Check for companion correlation codes; scope the cam signal while wiggling the harness.
Repair options & costs
| Repair | Shop total (parts + labor) | DIY (parts only) | Difficulty |
|---|---|---|---|
| Camshaft position sensor | $90 – $255 | $40 – $130 (parts only) | 2/5 |
National ranges from Number Nest's cost model (midsize car, independent shop, US-average labor).
OBDex repair data for this code rates the job difficulty easy with a typical labor time in the 0.3–2 hour range and DIY possible: yes.
Price this repair in your state
Estimated total: — (midsize car, independent shop)
Frequently asked questions
Will the car start with a dead cam sensor?
Many engines will, on a longer crank, falling back to crank-based timing; some will not. Either way, expect rough running and stalling risk — do not plan trips around it.
How much does it cost to fix P0340?
The fix most associated with this code — camshaft position sensor — runs $90 – $255 at an independent shop for a midsize car in our cost model (parts + labor, US average). The code names a system, not a part, so confirm the cause before spending: the ranked causes above are ordered by likelihood.
Can I drive with P0340?
See the can-you-drive verdict above — it is based on the system involved and the cascading-damage risk, and it is our editorial triage, not a manufacturer instruction. If the light is flashing or the car feels unsafe, stop driving it regardless of any code.
Will P0340 clear itself?
If the fault was a one-off (a loose cap, a cold-start glitch), the light can go out after several clean trips and the code ages into history. A fault that is still present re-sets the code as soon as the car runs that self-test again — monitors run under specific conditions, which is why "it hasn't come back in two days" is not proof of a fix.
Will my car fail inspection with P0340?
In states with OBD-based emissions inspection, yes — an illuminated check-engine light or an incomplete readiness monitor fails the test regardless of what the tailpipe would show. C-codes (ABS) fall under safety inspection instead in states that have one.
What should I check first for P0340?
The first item on the ranked-causes list above — it is ranked likelihood-first for exactly this reason — plus the free checks: recent work in the area (connectors left loose are a classic), fluid levels, and the battery and grounds on electrical codes.
Where this data comes from
Code facts, causes and symptoms come from OBDex — an open dataset of independently authored descriptions of the standardized generic OBD-II codes (CC0 1.0, public domain; github.com/foerbsnavi/OBDex). The SAE J2012 document itself is copyrighted and is not reproduced here. Cost ranges are Number Nest's own US planning model: national parts and labor ranges cross-checked against the CarMD Vehicle Health Index 2026 published averages, with labor adjustable by the BLS OEWS May 2025 state wage index for auto technicians (occupation 49-3023) — a wage index, not a surveyed shop rate. Severity and can-you-drive notes are our editorial triage, not a manufacturer instruction.