Pinpoint Test D: DTC B1251 Or B1253
Climate Control System
Pinpoint Tests
Pinpoint Test D: DTC B1251 or B1253
Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, the in-vehicle air temperature sensor receives a ground from the HVAC module. The sensor varies its resistance with the temperature. As the temperature rises, the resistance falls. As the temperature falls, the resistance rises. The HVAC module measures this resistance to determine the temperature at the sensor.
- DTC B1251 (Air Temperature Internal Sensor Circuit Open) - The module senses no voltage drop on the sensor reference voltage circuit, indicating an open circuit.
- DTC B1253 (Air Temperature Internal Sensor Circuit Short to Ground) - The module senses excessive voltage drop on the sensor reference voltage circuit, indicating a short directly to ground.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- In-vehicle air temperature sensor
- HVAC module
PINPOINT TEST D: DTC B1251 OR B1253
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D1 CHECK THE SENSOR RESISTANCE
- Ignition OFF.
- Disconnect: In-Vehicle Temperature Sensor C233.
- Measure the resistance between the in-vehicle temperature sensor terminals.
- Is the resistance within the specified values for these temperature ranges: 10-20°C (50-68°F), 37,000-58,000 ohms; 20-30°C (68-86°F), 24,000-37,000 ohms; 30-40°C (86-104°F), 16,000-24,000 ohms?
Yes
GO to D2.
No
INSTALL a new in-vehicle temperature sensor. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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D2 CHECK THE HVAC SENSOR OUTPUT VOLTAGE
- Ignition ON.
- Press the AUTOMATIC button.
- Measure the voltage between the in-vehicle temperature sensor C233-1, circuit 3060 (GY/RD), harness side and C233-2, circuit 3059 (YE/LG), harness side.
- Is the voltage between 4.7 and 5.1 volts?
Yes
INSTALL a new in-vehicle temperature sensor. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation. If the code returns, GO to D7.
No
If diagnosing DTC B1251, GO to D3.
If diagnosing DTC B1253, GO to D5.
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D3 CHECK CIRCUIT 3060 (GY/RD) FOR AN OPEN
- Ignition OFF.
- Disconnect: HVAC Module C228B.
- Measure the resistance between HVAC module C228B-21, circuit 3060 (GY/RD), harness side and in-vehicle temperature sensor C233-1, circuit 3060 (GY/RD), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to D4.
No
REPAIR circuit 3060 (GY/RD) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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D4 CHECK CIRCUIT 3059 (YE/LG) FOR AN OPEN
- Disconnect: HVAC Module C228A.
- Measure the resistance between HVAC module C228A-4, circuit 3059 (YE/LG), harness side and in-vehicle temperature sensor C233-2, circuit 3059 (YE/LG), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to D7.
No
REPAIR circuit 3059 (YE/LG) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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D5 CHECK CIRCUITS 3060 (GY/RD) AND 3059 (YE/LG) FOR A SHORT TOGETHER
- Ignition OFF.
- Disconnect: HVAC Module C228B.
- Measure the resistance between in-vehicle temperature sensor C233-1, circuit 3060 (GY/RD), harness side and C233-2, circuit 3059 (YE/LG), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to D6.
No
REPAIR circuit 3059 (YE/LG) for a short to circuit 3060 (GY/RD). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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D6 CHECK CIRCUIT 3060 (GY/RD) FOR A SHORT TO GROUND
- Measure the resistance between HVAC module C228B-21, circuit 3060 (GY/RD), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to D7.
No
REPAIR circuit 3060 (GY/RD) for a short to ground. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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D7 CHECK THE HVAC MODULE CONNECTION
- Inspect the module connectors for:
- corrosion.
- pushed-out terminals.
- damaged terminals.
- Connect and correctly seat all the HVAC module connectors.
- Clear the DTCs.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new HVAC module. REFER to Climate Control Heating Ventilation Air Conditioning (HVAC) Module. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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