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.
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HOMESERVICE MANUALSCHEVROLET2001CHEVY EXPRESS G2500, VAN CARGO EXTENDED, 5.7 R, L31/KL8REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 234 (ENGINE CONTROLS - SELF-DIAGNOSTICS)DIAGNOSTIC TESTSDTC P0420: TWC SYSTEM - LOW EFFICIENCYCONDITIONS FOR RUNNING DTC
2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8
Conditions For Running DTC
2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8SECTION Conditions For Running DTC
WARNING: This page is about a different car, the 2003 Cadillac Seville and 2003 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
- DTCs P0030, P0036, P0101, P0102, P0103, P0106-P0108, P0112, P0113, P0116-P0118, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0150, P0151, P0152, P0153, P0154, P0155, P0171, P0172, P0174, P0175, P0201-P0208, P0300, P0335, P0336, P0340, P0341, P0351-P0358, P0385, P0386, P0404, P0405, P0410, P0412, P0418, P0440, P0442, P0443, P0446, P0449, P0452, P0453, P0502, P0503, P0506, P0507, P1031, P1032, P1133, P1134, P1336, P1359, P1360, P1372, P1415-P1416, P1441, P1153, or P1154 are not set.
- The engine speed since the end of the last idle period is more than 800 RPM for a maximum of 46 seconds.
- The idle period is less than 60 seconds.
- The actual engine speed is within 100 RPM of desired engine speed (Non-California).
- The actual engine speed is within 125 RPM of desired engine speed (California).
- The engine run time is more than 10 minutes.
- The predicted catalyst temperature is 788-1202°F (420-650°C).
- The Barometric (BARO) pressure is more than 75 kPa.
- The Engine Coolant Temperature (ECT) is 160-248°F (71-120°C).
- The Intake Air Temperature (IAT) is 21-329°F (-6-200°C).
- The engine is in Closed Loop fuel control.
- Tests attempted this ignition cycle is less than 6.
- Test attempted during idle period is 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.