Pinpoint Test C: DTC B1251 Or B1253
Climate Control System
Pinpoint Tests
Pinpoint Test C: 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 - Dual Automatic Temperature Control (DATC) through circuit RH111 (GY/BU). A 5-volt reference voltage is supplied to the in-vehicle air temperature sensor from the HVAC module - DATC through circuit VH414 (GN/BU).
- 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 - DATC
PINPOINT TEST C: DTC B1251 OR B1253
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C1 CHECK THE SENSOR RESISTANCE
- Ignition OFF.
- Disconnect: In-Vehicle Temperature Sensor C233.
- Measure the resistance between the in-vehicle temperature sensor C233 terminals and compare to the table below.
- Is the resistance within the specified values for the temperatures?
Yes
GO to C2.
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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C2 CHECK THE SENSOR OUTPUT VOLTAGE
- Ignition ON.
- Press the AUTO button.
- Measure the voltage between in-vehicle temperature sensor C233-1, circuit VH414 (GN/BU), harness side and C233-2, circuit RH111 (GY/BU), harness side.
- Is the voltage between 4.7 and 5.1 volts?
Yes
INSTALL a new in-vehicle sensor. CLEAR the DTCs. REPEAT the self test. If code returns, GO to C7.
No
If diagnosing DTC B1251, GO to C3.
If diagnosing DTC B1253, GO to C5.
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C3 CHECK CIRCUIT VH414 (GN/BU) FOR AN OPEN
- Ignition OFF.
- Disconnect: HVAC Module - DATC C228a.
- Measure the resistance between HVAC module - DATC C228a-3, circuit VH414 (GN/BU), harness side and in-vehicle temperature sensor C233-1, circuit VH414 (GN/BU), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to C4.
No
REPAIR circuit VH414 (GN/BU) for an open. CLEAR the DTCs. REPEAT the self test. TEST the system for normal operation.
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C4 CHECK CIRCUIT RH111 (GY/BU) FOR AN OPEN
- Measure the resistance between HVAC module - DATC C228a-10, circuit RH111 (GY/BU), harness side and in-vehicle temperature sensor C233-2, circuit RH111 (GY/BU), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to C7.
No
REPAIR circuit RH111 (GY/BU) for an open. CLEAR the DTCs. REPEAT the self test. TEST the system for normal operation.
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C5 CHECK CIRCUIT VH414 (GN/BU) FOR A SHORT TO CIRCUIT RH111 (GY/BU)
- Ignition OFF.
- Disconnect: HVAC Module - DATC C228b.
- Measure the resistance between in-vehicle temperature sensor C233-1, circuit VH414 (GN/BU), harness side and C233-2, circuit RH111 (GY/BU), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to C6.
No
REPAIR circuit VH414 (GN/BU) for a short to circuit RH111 (GY/BU). CLEAR the DTCs. REPEAT the self test. TEST the system for normal operation.
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C6 CHECK CIRCUIT VH414 (GN/BU) FOR A SHORT TO GROUND
- Measure the resistance between HVAC module - DATC C228a-3, circuit VH414 (GN/BU), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to C7.
No
REPAIR circuit VH414 (GN/BU) for a short to ground. CLEAR the DTCs. REPEAT the self test. TEST the system for normal operation.
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C7 CHECK THE MODULE CONNECTION
- Carry out the HVAC Module Cold Boot Process. HVAC Module Cold Boot Process
- Carry out the HVAC Module - Dual Automatic Temperature Control (DATC) On-Demand Self Test. Alternate Diagnostic Methods - HVAC Module - Dual Automatic Temperature Control (DATC) Only
- Operate the system.
- Does the concern return?
Yes
INSTALL a new HVAC module - DATC. 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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