P0430

P0430-CATALYST 2/1 EFFICIENCY

P0430 - Catalyst 2/1 Efficiency:

Theory of Operation
The upstream O2 sensor is used to detect the amount of oxygen in the exhaust gas before the gas enters the catalytic converter. During the catalyst/O2 monitor test, the response rate (cycles/second) of the upstream O2 sensor determines the sensor's ability to achieve the tailpipe emissions limits. The response rate of the downstream O2 sensor relative to the upstream O2 sensor response rate measures the catalyst's ability to store oxygen and is used to infer the catalyst's ability to achieve the tailpipe emissions limits.

WHEN MONITORED
After engine warm up to 147 deg. F, 180 seconds of open throttle operation, at a speed greater than 20 mph, with the engine at 1200-1700 rpm and MAP vacuum between 15.0 and 21.0 inches of mercury (Hg).

SET CONDITION
As catalyst efficiency deteriorates, the switch rate of the downstream O2 sensor approaches that of the upstream O2 sensor. If at any point during the test the switch ratio reaches a predetermined value a counter is incremented by one. Three good trips to turn off the MIL.

POSSIBLE CAUSES
- Exhaust leak
- Engine mechanical
- Aging O2 sensor
- Catalytic converter

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test

1. ACTIVE DTC

NOTE:
- A new rear O2 Sensor along with an aging front O2 Sensor may cause the DTC to set. Review the repair history of the vehicle before continuing.
- If an O2 Sensor DTC set along with the Catalytic Converter Efficiency DTC diagnose the O2 Sensor DTC(s) before continuing.
- Check for contaminants that may have damaged the O2 Sensor and Catalytic Converter: contaminated fuel, unapproved silicone, oil and coolant, repair necessary.

Ignition on, engine not running.
With a scan tool, read DTCs.

Q: Is the DTC active at this time?

YES: Go To 2
NO: Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

2. VISUALLY INSPECT CATALYTIC CONVERTER
Inspect the Catalytic Converter for the following damage.
Damaged Catalytic Converter, dents or holes.
Severe discoloration caused by overheating the Catalytic Converter.
Catalytic Converter broken internally.
Leaking Catalytic Converter.

Q: Were any problems found?

YES: Replace the Catalytic Converter. Repair the condition that may have caused the failure. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 3

3. EXHAUST LEAK
Start the engine.
Inspect the exhaust for leaks between the engine and the 2/1 O2 Sensor.
Inspect the exhaust for leaks between the engine and the 2/2 O2 Sensor.

Q: Are there any exhaust leaks?

YES: Repair or replace the leaking exhaust parts as necessary. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 4

4. ENGINE MECHANICAL
Check the exhaust for excessive smoke caused by an internal problem in the engine.

Q: Is an engine mechanical condition present?

YES: Repair the engine mechanical condition as necessary. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 5

5. AGING O2 SENSOR
A new rear O2 Sensor along with an aging front O2 Sensor may cause the DTC to set.
Review the vehicles repair history.

Q: Has the rear O2 Sensor been replaced without replacing the front O2 Sensor?

YES: Replace the 2/1 O2 Sensor as necessary. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 6

6. CATALYTIC CONVERTER
If there are no possible cause remaining, view repair.

Repair

Replace the Catalytic Converter.
Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test