The CMP sensor in Honda vehicles is the Camshaft Position Sensor. It helps the engine computer time the fuel injection and ignition by monitoring the camshaft’s position. If the CMP sensor isn’t functioning, the engine may run poorly or fail to start.
Honda uses the CMP sensor to detect the camshaft’s position relative to the crankshaft. The engine control module uses this data to synchronize valve timing, ignition timing, and fuel delivery, particularly on engines with variable valve timing or VTEC. This article explains what the CMP sensor does, where to find it on common Honda engines, typical failure signs, how it’s tested, and what owners should know about replacement.
What the CMP sensor does
The camshaft position (CMP) sensor provides a reference signal to the engine control unit (ECU) indicating the camshaft’s position. The ECU uses this information, in concert with the crankshaft position (CKP) sensor, to time ignition and fuel injection and to manage variable valve timing systems on many Honda engines.
Where it's located
Location varies by engine family and year; below are typical spots found on common Honda engines. Use the service manual for exact location on your model.
- Near the cylinder head, aligned with the camshaft gear or pulley on timing belt/chain setups
- Under the valve cover area on some older or inline engines
- On newer engines, integrated into the cylinder head near the camshaft or behind the timing belt cover
Locating the CMP sensor requires engine-specific diagrams. If you’re unsure, consult a Honda service manual or a qualified technician.
Common symptoms of a failing CMP sensor
Watch for indicators that the cam position reference is failing. These signs can overlap with issues from the CKP sensor or wiring, so thorough diagnosis is recommended.
- Hard starts or no-start conditions
- Rough idling, misfires, or stalling
- Inconsistent or poor acceleration
- Check Engine Light with codes such as P0340 or P0341 depending on generation
- Timing-related issues with EFI or VTEC operation
Note: The exact symptom pattern depends on model and the ECU logic used in that variant. A scan and inspection are necessary to confirm CMP health.
How to diagnose and replace
Steps to confirm a CMP issue and replace if necessary. Include checking wiring and related sensors as part of the diagnostic process.
- Read engine codes with an OBD-II scanner to identify P0340/P0341 or related camshaft-position codes.
- Visually inspect the sensor and its wiring harness for damage, corrosion, or loose connectors.
- Check the sensor’s electrical resistance and signal continuity with a multimeter, or use an oscilloscope to examine the sensor waveform if available.
- Inspect the CKP sensor and timing components (timing belt/chain, tensioners, pulleys) to rule out timing issues.
- If the signal is absent or out of spec and wiring is sound, replace the CMP sensor with an OEM or high-quality aftermarket unit designed for your engine family.
- Clear codes, reconnect the battery, and perform a road test to verify proper operation and timing.
After replacement, verify there are no residual codes and that engine timing-related functions, including idle and startup, return to normal.
Notes on compatibility and replacement
Honda CMP sensors vary by engine family (D-series, B-series, K-series, and newer platforms). Use the correct part number for your vehicle, and be aware that some engines use a single sensor that handles multiple timing references, while others have separate sensors. OEM parts are recommended for reliability.
Summary
The CMP sensor, or camshaft position sensor, is a critical engine sensor in most Honda vehicles. It provides the ECU with accurate camshaft position data to control ignition timing, fuel delivery, and variable valve timing. If it fails, you may experience starting problems, stalling, misfires, or limp-mode operation. Proper diagnosis should confirm CMP sensor health before replacement, and wiring or timing issues should be checked as well.