07-02 Confirmed

ECT sensor circuit high voltage

The coolant temperature sensor read too high, as if its circuit is open, and stayed that way long enough to count as a real fault.

Manufacturer: Honda
Platform: PGM-FI (Keihin, Renesas M32R)
Models: CBR600RR
Years: 2003-2022
Subsystem: ECT (coolant temperature) sensor
Hex: 0x0702

Confirmed. Confirmed: how the ECU detects this was traced in the firmware and matches the standard Honda meaning of the code.

What it means

Same coolant sensor check as 07-01, but the signal sat above the high limit. An open sensor or wire floats the reading high, so this is a high-voltage circuit fault.

Conditions

Detection conditions

The ECU reads the coolant 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

Engine coolant temperature (ECT) sensor
Its signal and ground wiring

Symptoms & likely causes

Possible symptoms

FI (check-engine) light on
A default temperature is used, so cold running or fan behaviour may be off

Likely causes

Open coolant sensor signal or ground wire
Failed (open) coolant sensor
Disconnected connector

Diagnostic guidance

A high reading points to an open circuit. Check for a broken signal or ground wire, or a disconnected sensor, before replacing it.

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

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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