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HOMESERVICE MANUALSTOYOTA19994RUNNER LIMITED, 3.4 N, RWDREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM SELF-DIAGNOSTICS - V6DIAGNOSTIC TESTSDTC P1135: AIR/FUEL SENSOR HEATER CIRCUIT (CALIF. EMISSIONS)DIAGNOSIS & REPAIR
1999 Toyota 4Runner Limited, 3.4 N, RWD

Diagnosis & Repair

1999 Toyota 4Runner Limited, 3.4 N, RWDSECTION Diagnosis & Repair
  1. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe at ECM harness connector and measure voltage between ground and terminal No. 4 (Blue wire) at ECM harness connector E10. See Figure. If voltage is 9-14 volts, replace ECM. If voltage is not 9-14 volts, go to next step.
  2. Disconnect A/F sensor harness connector. Measure resistance between terminal B+ (White/Blue wire) and HT (Blue wire ) at A/F sensor connector (component side). See Figure. Resistance should be .8-1.4 ohms at 68°F (20°C) and 1.8-3.2 ohms at 1472°F (800°C). If resistance is not as specified, replace A/F sensor. If resistance is as specified, go to next step.
  3. Check for open or short in wiring between EFI main relay and A/F sensor, and between A/F sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
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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.