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 P00B3 00: Radiator Coolant Temperature (RCT) Sensor Circuit Low Voltage
DTC P00B4 00: Radiator Coolant Temperature (RCT) Sensor Circuit High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to voltage | Signal Performance
--- | --- | --- | --- | ---
RCT signal circuit | P0033 00 | P00B4 00 | P00B4 00* | P00B6 00
Low reference | -- | P00B4 00 | P00B4 00* | P00B6 00
* Internal ECM or sensor damage may occur if the circuit is shorted to B+.

### Typical Scan Tool Data

#### RCT Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Engine operating in closed loop Parameter Normal Range: Varies with ambient temperature
RCT sensor signal | 150°C (302°F) | -40°C (-40°F)* | -40°C (-40°F)*
Low reference | -- | -40°C (-40°F)* | -40°C (-40°F)*
* Internal ECM or sensor damage may occur if the circuit is shorted to B+.

### Circuit/System Description

The engine coolant temperature (ECT) sensor 2 is a variable resistor that measures the temperature of the engine coolant in the radiator. The engine control module (ECM) supplies 5 V to the engine coolant temperature (ECT) sensor 2 signal circuit and supplies a ground to the low reference circuit.

The following table illustrates the difference between temperature, resistance, and voltage:

RCT | RCT resistance | RCT signal voltage
--- | --- | ---
Cold | High | High
Warm | Low | Low

### Conditions for Running the DTC

#### P00B3

• | DTCs P0112 00 or P0113 00 are not set.

• | The engine run time is greater than 10 s.

• | The intake air temperature (IAT) is less than 70°C (158°F).

• | The DTCs run continuously when the above conditions are met.

#### P00B4

• | DTCs P0112 00 or P0113 00 are not set.

• | The engine run time is greater than 60 s.

• | The intake air temperature (IAT) is less than -7°C (19°F).

• | The DTCs run continuously when the above conditions are met.

### Conditions for Setting the DTC

#### P00B3 00

The ECM detects that the engine coolant temperature (ECT) sensor 2 is greater than 149°C (300°F) for greater than 5 s.

#### P00B4 00

Note: The scan tool only displays to -40°C (-40°F).

The ECM detects that the engine coolant temperature (ECT) sensor 2 is colder than -60°C (-76°F) for greater than 5 s.

### Action Taken When the DTC Sets

• | DTCs P00B3 00 and P00B4 00 are Type B DTCs.

• | The cooling fans will be commanded ON by the ECM.

### Conditions for Clearing the DTC

DTCs P00B3 00 and P00B4 00 are Type B DTCs.

### Diagnostic Aids

Note: The engine coolant temperature (ECT) sensor 1 is mounted on the engine and the engine coolant temperature (ECT) sensor 2 (radiator coolant temperature (RCT) sensor) is mounted on the radiator.

• | As the thermostat opens, the engine coolant temperature (ECT) sensor 2 temperature should rise steadily, then stabilize once the thermostat opens completely.

• | Test the engine coolant temperature (ECT) sensor 2 at various temperature levels in order to evaluate the possibility of a skewed sensor.

• | If the vehicle has sat overnight, the engine coolant temperature (ECT) sensor 2 and the engine coolant temperature (ECT) sensor 1 values should display within 3°C (5°F).

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### 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

Note: The intake air temperature must be between -7 to +70°C (19 to 158°F) for the DTCs to set.

1. Engine idling, observe the DTC information with a scan tool. DTC P00B3 00 or P00B4 00 should not set.
2. Operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that you observed from the freeze frame / failure records data.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B34B Engine Coolant Temperature (ECT) Sensor 2.
2. Ignition OFF for 1 m, test for less than 5 Ω between the ground circuit terminal 1 and ground.

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

3. Ignition ON, verify the scan tool ECT Sensor 2 sensor parameter is at -40°C (-40°F).

⇒ | If greater than the specified range, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

Note: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage and the sensor may be damaged.

4. Install a 1 A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2. Verify the ECT Sensor 2 sensor parameter is at 150°C (302°F).

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

5. If all circuits test normal, test or replace the B34B Engine Coolant Temperature (ECT) Sensor 2.

### Component Testing

#### Static Test

1. Ignition OFF, disconnect the harness connector at the B34B Engine Coolant Temperature (ECT) Sensor 2.

Note: A thermometer can be used to test the sensor off the vehicle.

2. Test the B34B Engine Coolant Temperature (ECT) Sensor 2 by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the LINK (Temperature Versus Resistance) table and verify that the resistance is within 5% of the specification.

⇒ | If not within the specified range, replace the B34B Engine Coolant Temperature (ECT) Sensor 2.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Engine Coolant Temperature Sensor Replacement

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