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Exhaust System Backpressure

CAUTION: While engine is operating, exhaust system will become extremely hot. To prevent burns, avoid contacting a hot exhaust system.
NOTE: When performing exhaust system backpressure test, ensure transmission is in Neutral or Park. Accurate readings cannot be obtained unless vehicle remains in Neutral or Park. For dual exhaust systems, a quick check of exhaust flow will help determine which side of exhaust system is restricted. The side that has less exhaust flow is side that will be suspect, and diagnosis should begin there.
    NOTE: Exhaust system has very low backpressure under normal conditions. If exhaust system is restricted, a significant increase in exhaust backpressure is noticed on exhaust backpressure gauge. Removing HO2S may set a DTC. When testing is finished, ensure all DTCs have been cleared.
  1. Remove pre-catalyst HO2S that is in front of and closest to catalytic converter. Install Exhaust Back Pressure Gauge (J 35314-A) in place of HO2S. Start engine and allow it to idle. With engine idling at normal operating temperature, record exhaust system backpressure reading on gauge. If pressure is 1.25 psi (8.6 kPa) or less, go to next step. If pressure is more than 1.25 psi (8.6 kPa), go to step  3.
    2. NOTE: If high backpressure is not found at idle, increasing engine speed may help find a restriction.
  2. Increase engine speed to 2000 RPM and monitor backpressure reading on exhaust backpressure gauge. If pressure is more than 1.25 psi (8.6 kPa), go to next step. If pressure is 1.25 psi (8.6 kPa) or less, go to step  6.
  3. Turn ignition off. Remove exhaust backpressure gauge. Install pre-catalyst HO2S. Remove post-catalyst HO2S. Install exhaust backpressure gauge in place of post HO2S. Start engine and allow it to idle. Raise engine speed to 2000 RPM. Observe exhaust system backpressure gauge reading. If pressure is more than 1.25 psi (8.6 kPa), go to next step. If pressure is 1.25 psi (8.6 kPa) or less, go to step  5.
  4. Check entire exhaust system for collapsed pipe, heat distress or possible internal muffler failure. Repair as necessary. After repairs, go to step  6.
  5. Replace catalytic converter. After repairs, go to next step.
  6. Remove exhaust backpressure gauge and install HO2S. Check for DTCs. If no DTCs are set, system is okay. If DTCs are set, perform appropriate diagnostic procedure for DTC set. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.0L TRACKER article or DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 2.5L TRACKER.
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