IAT sensor circuit high voltage
The intake air temperature sensor read too high, as if its circuit is open. This is the standard Honda meaning for the code.
- Manufacturer
- Honda
- Platform
- PGM-FI (Keihin, Renesas M32R)
- Models
- CBR600RR
- Years
- 2003-2022
- Subsystem
- IAT (intake air temperature) sensor
- FI-light blink
- 9 short
- Hex
- 0x0902
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
Same intake-air-temperature check as 09-01, but the signal sat too high, the pattern of an open circuit.
Conditions
Detection conditions
- The ECU reads the intake air temperature sensor against a normal range.
Sets the fault when
- The signal stays above the high limit long enough to rule out brief noise.
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
- Intake air temperature (IAT) sensor
- Its signal and ground wiring
Symptoms & likely causes
Possible symptoms
- FI (check-engine) light on
- A default air temperature is used
Likely causes
- Open IAT signal or ground wire
- Failed (open) IAT sensor
- Disconnected connector
Diagnostic guidance
Diagnose as a high-voltage intake-air-temperature circuit 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.
The ECU checks each sensor against a normal high and a normal low value. A brief spike is ignored; only a reading that stays out of range long enough counts as a real fault. Too low sets the "-01" (low) code, too high sets the "-02" (high) code.
// A sensor reading outside its normal band, held long enough to be real.
if (reading < low_limit || reading > high_limit) {
bad_count++; // ignore brief electrical noise
if (bad_count >= limit)
set_fault(); // low -> "-01", high -> "-02"
} else {
bad_count = 0; // back in range: no fault
}
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 09-02
- What does Honda code 09-02 mean?
- The intake air temperature sensor read too high, as if its circuit is open. This is the standard Honda meaning for the code.
- Which motorcycles does code 09-02 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 09-02?
- It depends on the fault. Code 09-02 relates to the IAT (intake air temperature) 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 09-02?
- Diagnose as a high-voltage intake-air-temperature circuit 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.