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Home >> Toyota >> 1999 >> Celica 2D Convertible, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics >> Diagnostic Tests >> DTC P0450: EVAP Pressure Sensor Circuit, Or DTC P0451: EVAP Pressure Sensor Range/Performance >> Diagnosis & Repair
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Diagnosis & Repair

  1. Access ECM below passenger's side of instrument panel, underneath carpet near center console. Turn ignition on. Using DVOM, backprobe and measure voltage between terminals No. 1 (Red wire) and No. 9 (Brown wire) at ECM harness connector E6. See Figure. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, replace ECM.
  2. Using DVOM, backprobe ECM connector and measure voltage between terminals No. 7 (Red/White wire) and No. 9 (Brown wire) at ECM harness connector E6. Disconnect vacuum hose from vapor pressure sensor. Connect a vacuum pump to vapor pressure sensor. Voltage should be 2.9-3.7 volts without vacuum applied and less than .5 volt with 1.18 in. Hg applied. If voltage is as specified, replace ECM. If voltage is not as specified, go to next step.
  3. Check for open or short in wiring between vapor pressure sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, replace vapor pressure sensor.
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