CMP sensor no signal
The ECU saw no camshaft-position signal when it expected one. This is the standard Honda meaning for the code.
- Manufacturer
- Honda
- Platform
- PGM-FI (Keihin, Renesas M32R)
- Models
- CBR600RR
- Years
- 2003-2022
- Subsystem
- CMP (camshaft position) sensor
- FI-light blink
- 1 long, 8 short
- Hex
- 0x1801
Strongly inferred. Strongly inferred: the standard Honda meaning is well established, but exactly how this ECU handles it internally is inferred rather than fully confirmed.
What it means
The camshaft position sensor helps the ECU know which cylinder is which. This code sets when its signal is missing while the engine is cranking or running, which can upset timing and, in the worst case, cause a no-start.
Conditions
Detection conditions
- The ECU expects a cam signal during cranking or running but does not see it.
Sets the fault when
- The cam signal is absent long enough to count.
Clears the fault when
- Fix the underlying problem, then clear the stored codes with a diagnostic tool or the manufacturer’s reset procedure. If the fault is still present, the code returns the next time the ECU detects it.
Parts involved
- Camshaft position (CMP) sensor
- Its signal wiring and trigger wheel
Symptoms & likely causes
Possible symptoms
- FI (check-engine) light on
- Hard starting or, in the worst case, a no-start
Likely causes
- CMP signal open or shorted
- Failed CMP sensor
- Sensor air-gap or trigger-wheel problem
Diagnostic guidance
If you also have a crank-sensor code, diagnose the two together when chasing a sync or no-start fault.
How the ECU decides
A simplified view of the logic behind this code: a short C snippet with a plain-English summary. It shows the real decision the ECU makes without the low-level detail.
When the ECU confirms a fault, it saves the code and turns on the FI (check-engine) light. For a serious fault it also runs the engine on safe default values (limp-home) so you can still ride, with the light on.
// Once a fault is confirmed, remember it and warn the rider.
if (fault_confirmed) {
store_code(code); // kept until the codes are cleared
fi_light = ON;
if (fault_is_serious)
limp_home = ON; // safe defaults so you can ride home
}
Related codes
Questions about code 18-01
- What does Honda code 18-01 mean?
- The ECU saw no camshaft-position signal when it expected one. This is the standard Honda meaning for the code.
- Which motorcycles does code 18-01 apply to?
- It is documented here for the Honda CBR600RR (2003-2022). Other Honda models may use the same display code with a different meaning, so confirm against your model.
- Can I still ride with code 18-01?
- It depends on the fault. Code 18-01 relates to the CMP (camshaft position) sensor. If the bike runs poorly or a safety-related system is affected, avoid riding until it is checked. The FI light stays on until the fault is fixed and the codes are cleared.
- What should I check first for code 18-01?
- If you also have a crank-sensor code, diagnose the two together when chasing a sync or no-start fault.
Sources
Every technical claim on this page traces to the research below. Source labels are sanitized; no local research paths are exposed.
- firmware
2005-2006 Honda CBR600RR ECU firmware
Factory PGM-FI firmware for the 2005-2006 CBR600RR. Primary source of truth.
- analysis
Firmware fault-code table extraction
Reads the list of codes the ECU can store directly out of each firmware.
- reference
HondaECU project (open-source Honda ECU tool)
Community reference mapping Honda PGM-FI codes to their meanings.
- analysis
CBR600RR ECU reverse-engineering analysis
Independent analysis of how the ECU detects, stores, and reports faults.