Which motorcycles does code 09-01 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 09-01?

It depends on the fault. Code 09-01 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.

09-01 Strongly inferred

IAT sensor circuit low voltage

The intake air temperature sensor read too low, as if its circuit is shorted. 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: 0x0901

Saw 09-01 as 9 short on the FI light? Decode a blink pattern →

All major 09 codes How blink codes work

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 intake air temperature sensor lets the ECU trim fuelling for hot or cold air. The ECU checks it against a normal range, and a reading stuck too low sets this low-voltage code. Effects are usually mild since this sensor only fine-tunes fuelling.

Conditions

Detection conditions

The ECU reads the intake air temperature sensor against a normal range.

Sets the fault when

The signal stays below the low 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; usually mild running effects

Likely causes

IAT signal shorted to ground
Failed (shorted) IAT sensor
Connector fault

Diagnostic guidance

Diagnose as a low-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.

C How an out-of-range sensor sets a code

1// A sensor reading outside its normal band, held long enough to be real.
2if (reading < low_limit || reading > high_limit) {
3    bad_count++;               // ignore brief electrical noise
4    if (bad_count >= limit)
5        set_fault();           // low -> "-01", high -> "-02"
6} else {
7    bad_count = 0;             // back in range: no fault
8}

Reverse-engineered interpretation · CBR600RR ECU reverse-engineering analysis

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.

C How a confirmed fault is stored

1// Once a fault is confirmed, remember it and warn the rider.
2if (fault_confirmed) {
3    store_code(code);      // kept until the codes are cleared
4    fi_light = ON;
5    if (fault_is_serious)
6        limp_home = ON;    // safe defaults so you can ride home
7}

Reverse-engineered interpretation · CBR600RR ECU reverse-engineering analysis

Related codes

Questions about code 09-01

What does Honda code 09-01 mean?: The intake air temperature sensor read too low, as if its circuit is shorted. This is the standard Honda meaning for the code.
Which motorcycles does code 09-01 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 09-01?: It depends on the fault. Code 09-01 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 09-01?: Diagnose as a low-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.

Content version 1.0.0 · last reviewed 2026-07-14

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