For 1990-2009 cars

### Circuit Description

In order to maintain a reasonably low emission level of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) a three-way catalytic converter is used. The catalyst within the converter promotes a chemical reaction that oxidizes the HC and CO present in the exhaust gas. This reaction converts the gases into harmless water vapor and carbon monoxide. The catalyst also reduces the NOx , converting the NOx, into nitrogen. The engine control module (ECM) monitors this process using the post catalyst heated oxygen sensor (HO2S) signal. The post catalyst HO2S, located in the exhaust stream after the three-way catalytic converter, produces an output signal that indicates the oxygen storage capacity of the catalyst. The catalyst's oxygen storage capacity determines the catalyst's ability to convert the exhaust emissions effectively. If the catalyst is functioning correctly, the post catalyst HO2S signal will be far less active than the signal produced by the pre-catalyst HO2S. If the ECM detects an excessive post catalyst signal activity (outside of an acceptable range) for an extended period of time, the ECM will set this DTC. This indicates that the three-way catalytic converter's oxygen storage capacity is below a threshold considered acceptable.

### Conditions for Running the DTC

• | None of the following DTCs are set: P0100, P0131, P0132, P0134, P0135, P0136, P0138, P0139, P0140, P0141, P0150, P0151, P0152, P0154, P0155, P0156, P0158, P0159, P0160, P0161, P0171, P0172, P0174, P0175, P0300-P0306, P0440, P0442, P0443, P0446, P0455, P1120 or P1220.

• | The engine is operating in closed loop.

• | The calculated three-way catalytic converter TWC temperature is greater than 380°C (716°F).

• | The engine load is between 8 and 12 percent.

• | The engine speed is between 1400-2200 RPM.

### Conditions for Setting the DTC

• | The amplitude ratio, rear HO2S to front HO2S, must be more than a predetermined value.

• | The above conditions are met for about 5 minutes.

### Action Taken When the DTC Sets

The ECM illuminates the malfunction indicator lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails.

### Conditions for Clearing the MIL/DTC

• | The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes.

• | A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic.

• | The ECM battery voltage is interrupted.

• | The scan tool clears the MIL/DTC.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. Before replacing the three way catalytic (TWC) converter, correct any conditions which may have caused the catalyst to be damaged.

#### DTC P0432 TWC System Low Efficiency Bank2

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Are any other DTCs set? | -- | Go to the applicable DTC table | Go to Step 3
3 | Check for the following conditions:

• | Verify that the catalytic converter is an original equipment part.

• | Inspect the catalytic converter for damage (dents, severe discoloration caused by excessive temperature, holes, etc.).

• | Ensure that internal catalytic converter rattle caused by the damaged catalyst is not present.

• | Inspect the exhaust system for any leaks, damage, or loose or missing hardware (the area from the converter to the HO2S 2 primarily).

• | Insure that the HO2S 2 is secure and that the pigtail and the wiring are not damaged or contacting the exhaust.

Did you find and correct a problem?

--

Go to Step 5

Go to Step 4

4 | Replace the converter. Is the action complete? | -- | Go to Step 5 | --
5 |

1. Using the scan tool, clear the DTCs.
2. Start the engine.
3. Allow the engine to idle until the engine reaches the normal operating temperature.
4. Select DTC and the Specific DTC function.
5. Enter the DTC number that was set.
6. Operate the vehicle within the Conditions for Running this DTC until the scan tool indicates that the diagnostic Ran.

Does the scan tool indicate that the diagnostic Passed?

--

Go to Step 6

Go to Step 2

6 | Does the scan tool display any additional, undiagnosed DTCs? | -- | Go to the applicable DTC table | System OK