Pinpoint Test D: DTC B1251 Or DTC B1253
Climate Control System
Pinpoint Test D: DTC B1251 or DTC 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 through circuit 3059 (YE/LG). A 5-volt reference voltage is supplied to the in-vehicle air temperature sensor from the HVAC module through circuit 3060 (GY/RD).
- DTC B1251 In-Vehicle Temperature Sensor Open Circuit - The module senses no voltage drop on the sensor reference voltage circuit, indicating an open circuit.
- DTC B1253 In-Vehicle Temperature 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 DTC 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, INSTALL a new HVAC module. TEST the system for normal operation.
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 MODULE CONNECTION
- Carry out the HVAC Module Cold Boot Process. HVAC Module Cold Boot Process
- Carry out the HVAC Module On-Demand Self Test. HVAC Module Self-Test
- Operate the system.
- Does the concern return?
Yes
INSTALL a new 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. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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