For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptor

DTC P2A00 53: O2S Circuit Closed Loop Performance Sensor 1 Malfunction
DTC P2A00 54: O2S Circuit Closed Loop Performance Sensor 1 Malfunction

### Circuit/System Description

The heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the engine is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1 275 mV. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases toward 1 000 mV indicates a rich fuel mixture. An HO2S voltage that decreases toward 0 mV indicates a lean fuel mixture

### Conditions for Running the DTC

• | DTCs P0106, P0107, P0108, P0116, P0117, P0118, P0131, P0132, P0201, P0202, P0203, P0204, P1516, P2101, P2119, or P2176 are not set.

• | Ignition voltage is between 10-18 V

• | Engine speed is between 1 000-3 400 RPM

• | Airflow into the engine is between 4-30 g/s

• | Engine coolant temperature (ECT) is greater than 70°C (158°F)

• | Engine run time is greater than 100 s

• | DTC P2A00 runs continuously when the above conditions are met for greater than 5 s

### Conditions for Setting the DTC

The ECM detects that the HO2S 1 voltage is greater than 1 100 mV for greater than 20 s after closed loop is enabled.

### Action Taken When the DTC Sets

DTC P2A00 is a Type B DTC

### Conditions for Clearing the DTC

DTC P2A00 is a Type B DTC

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Engine Control Module Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. DTC P0030, P0053, P0131, P0132, P0134 or P0135 should not be set.

⇒ | If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle

2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Engine idling, move the HO2S 1 harness connector and the engine control module (ECM) harness connector while monitoring the HO2S 1 voltage parameter. Verify that the HO2S parameter does not change abruptly while moving the related harnesses.

⇒ | If the HO2S parameter does change abruptly while moving the related harnesses repair the circuit as necessary.

2. Ignition OFF, disconnect the harness connector at the B52A Heated Oxygen Sensor (HO2S).
3. Ignition OFF for 60 s, test for less than 5 Ω between the low reference circuit terminal 3 and ground.

⇒ | If greater than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

4. Ignition ON, test for 1.5-2.1 V between the signal circuit terminal 1 and ground.

⇒ | If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

5. Install a 3 A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 3. Engine running, verify the scan tool HO2S parameter is less than 60 mV.

⇒ | If greater than the specified value, replace the K20 Engine Control Module (ECM).

6. Verify none of the following conditions exist:

• | Water intrusion in the HO2S harness connector

• | Fuel that is contaminated--Refer to Contaminants-in-Fuel Diagnosis

7. If all circuits test normal, test or replace the B52A Heated Oxygen Sensor (HO2S).

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Heated Oxygen Sensor 1 Replacement

• | Control Module References for ECM replacement, setup and programming