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Exhaust System Backpressure

  1. Verify customer complaint to ensure possible cause is restricted exhaust. If vehicle is equipped with dual exhaust, determine which side has least exhaust flow as the starting point. Proceed to next step.
  2. Turn ignition off. Remove HO2S located in front of and nearest to catalytic converter. Install Exhaust Backpressure Tester (J-35314-A/BT-8515/BT-8515A) into HO2S opening. Start and warm engine to normal operating temperature. With engine idling, read backpressure gauge. If exhaust system pressure does not exceed 1.25 psi (0.09 kg/cm2 ), go to next step. If exhaust system pressure exceeds 1.25 psi (0.09 kg/cm2 ), go to step  4 .
  3. Increase engine speed to 2000 RPM with transaxle in Park or Neutral. If reading on gauge exceeds 1.25 psi (0.09 kg/cm2 ), go to next step. If reading on gauge does not exceed 1.25 psi (0.09 kg/cm2 ), go to step  7 .
  4. Turn engine off and place ignition in LOCK position. Remove backpressure gauge from HO2S opening and reinstall HO2S. Remove O2S located behind catalytic converter and install backpressure gauge in opening. Start engine. Check backpressure with engine at idle and with engine at 2000 RPM. If reading on gauge exceeds 1.25 psi (0.09 kg/cm2 ), go to next step. If reading on gauge does not exceed 1.25 psi (0.09 kg/cm2 ), go to step  6 .
  5. Inspect exhaust system for damage to exhaust pipe, debris in exhaust pipe, internal muffler failure and/or separation of 2-layer exhaust pipe. After repair or replacement of components, go to step  7 .
  6. Replace catalytic converter. After replacement, go to next step.
  7. Remove backpressure gauge and reinstall O2S. Connect scan tool to Data Link Connector (DLC) and clear any Diagnostic Trouble Codes (DTC). See SELF-DIAGNOSTICS - PRIZM article. Road test vehicle to verify repair. If condition is corrected, exhaust system is okay. If condition is still present, repeat test.
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