Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC P1165 (D16Y5 M/T): Primary Ho2S-1 Range/Performance Problem
Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING DTCS in SELF-DIAGNOSTICS - INTRODUCTION article. Start engine and run at 3000 RPM with no loads and transmission in Park or Neutral until radiator fan comes on. Connect SCS Service Connector (07PAZ-0010100). Test drive vehicle at a steady speed of 55 MPH in 5th gear until readiness code comes on. If DTC P1165 is not indicated, problem is intermittent. System is okay at this time. Check for poor connections or loose wires at HO2S-1 and PCM connectors. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If DTC P1164 is indicated, replace HO2S-1.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.