Page 133 - 2019 SHOP MANUAL CRF1000/A/D

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PGM-FI SYSTEM
DTC 21 (O2 SENSOR)

ECM/PCM

O2 SENSOR

Bl Bl

Gr Gr Gr/Bl

Probable cause
• Open or short circuit in the Black wire between the
ECM/PCM and O2 sensor
• Open circuit in the Gray or Gray/black wire between
the O2 sensor and ECM/PCM
• Faulty O2 sensor
• Faulty ECM/PCM
DTC 21-1 (O2 Sensor)

• Before starting the inspection, check for loose or
poor contact on the O2 sensor 4P (Black), ECM/PCM
33P (Black) and 33P (Gray) connectors, and
recheck the DTC.
1. Recheck DTC
Erase the DTC (page 4-6).
Start the engine and warm it up until the coolant
temperature is 80°C (176°F).
Stop the engine.
Check the DTC with the MCS.
Is the DTC 21-1 indicated?
YES – GO TO STEP 2.
NO – Intermittent failure
2. O2 Sensor Output Line Open Circuit Inspection
Turn the ignition switch OFF.
Disconnect the O2 sensor 4P (Black) connector [1] [2]
(page 2-17).
Disconnect the ECM/PCM 33P (Gray) connector
(page 4-39).
Check for continuity between the wire harness side
4P (Black) connector [1] and 33P (Gray) connector
[2].
TOOL: Bl
Test probe 07ZAJ-RDJA110 C19
Connection: Black – C19
Is there continuity?
YES – GO TO STEP 3.
NO – Open circuit in the Black wire

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