What Does P0340 Mean?
The ECM is not receiving a valid signal from the camshaft position (CMP) sensor on bank 1. This sensor works in conjunction with the crankshaft position sensor to determine which cylinder is on its compression stroke for sequential fuel injection and ignition timing. Without the CMP signal, the ECM may switch to a batch-fire or waste-spark mode, causing reduced efficiency, rough running, hard starting, or a no-start condition depending on the vehicle.
Safety Warning
Driving risk depends on severity. If the engine starts and runs in degraded mode (batch-fire), it is drivable but with reduced performance and increased emissions. If the vehicle does not start or stalls repeatedly, do not attempt to drive. A jumped timing chain can cause valve-to-piston contact on interference engines, making this potentially urgent.
Common Causes
35%
Failed camshaft position sensor (dead Hall-effect element or open internal circuit)
25%
Damaged, corroded, or disconnected CMP sensor wiring or connector
15%
Damaged or misaligned camshaft reluctor ring/target wheel preventing signal generation
15%
Timing chain/belt that has jumped or stretched, causing the camshaft position to be outside the expected window relative to the crankshaft
10%
ECM input circuit failure for the CMP sensor signal
Diagnostic Steps
1
Check for a CMP sensor signal on live data while cranking — most scan tools show CMP sync status; 'No Sync' confirms total signal loss.
2
Inspect the CMP sensor connector for oil contamination (common due to proximity to valve cover gaskets), corrosion, or damaged pins — many CMP sensor failures are actually oil-soaked connectors.
3
Measure voltage at the CMP sensor connector: verify 5V reference (or 12V for some sensors) and ground are present with the key on — missing reference voltage points to a wiring or ECM issue.
4
For Hall-effect sensors, use a multimeter on the signal wire to check for a switching signal (0V to 5V) while cranking — no switching confirms sensor failure if power and ground are present.
5
If sensor and wiring test good, inspect the camshaft reluctor ring/target for damage using a borescope through the sensor bore — missing or damaged target features will prevent signal generation.
6
Check timing chain/belt condition by comparing CKP and CMP correlation on an oscilloscope — a skipped timing chain will show the CMP signal phase-shifted from its expected position relative to the CKP signal.
Estimated Repair Cost
$100 - $800
Parts + labor, varies by vehicle and location
The ECM is not receiving a valid signal from the camshaft position (CMP) sensor on bank 1. This sensor works in conjunction with the crankshaft position sensor to determine which cylinder is on its compression stroke for sequential fuel injection and ignition timing. Without the CMP signal, the ECM ...
The most common cause of P0340 (Camshaft Position Sensor Circuit Malfunction (Bank 1)) is: Failed camshaft position sensor (dead Hall-effect element or open internal circuit)
Typical repair costs for P0340 range from $100 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Driving risk depends on severity. If the engine starts and runs in degraded mode (batch-fire), it is drivable but with reduced performance and increased emissions. If the vehicle does not start or stalls repeatedly, do not attempt to drive. A jumped timing chain can cause valve-to-piston contact on interference engines, making this potentially urgent.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0340 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Ignition System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
