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 - Dual Automatic Temperature Control (DATC) through circuit RH104 (BU/BN). 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 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
GO to D7.
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D2 CHECK THE HVAC MODULE SENSOR OUTPUT VOLTAGE
- Ignition ON.
- Press the AUTOMATIC button.
- Measure the voltage between in-vehicle temperature sensor C233-1, circuit VH414 (GN/BU), harness side and C233-2, circuit RH104 (BU/BN), harness side.
- Is the voltage between 4.7 and 5.1 volts?
Yes
INSTALL a new in-vehicle temperature sensor. TEST the vehicle for normal operation. If code returns, INSTALL a new HVAC module - DATC. TEST the system for normal operation.
No
For DTC B1251, GO to D3.
For DTC B1253, GO to D5.
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D3 CHECK CIRCUIT VH414 (GN/BU) FOR AN OPEN
- Ignition OFF.
- Disconnect: HVAC Module - DATC C228a.
- Measure the resistance between HVAC module - DATC C228a-7, 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 D4.
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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D4 CHECK CIRCUIT RH104 (BU/BN) FOR AN OPEN
- Measure the resistance between HVAC module - DATC C228a-6, circuit RH104 (BU/BN), harness side and in-vehicle temperature sensor C233-2, circuit RH104 (BU/BN), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to D7.
No
REPAIR circuit RH104 (BU/BN) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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D5 CHECK CIRCUITS VH414 (GN/BU) AND RH104 (BU/BN) FOR A SHORT TOGETHER
- Ignition OFF.
- Disconnect: HVAC Module - DATC C228a.
- 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 RH104 (BU/BN), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to D6.
No
REPAIR circuits VH414 (GN/BU) and RH104 (BU/BN) for a short together. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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D6 CHECK CIRCUIT VH414 (GN/BU) FOR A SHORT TO GROUND
- Measure the resistance between ground and HVAC module - DATC C228a-7, circuit VH414 (GN/BU), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to D7.
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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D7 CHECK MODULE CONNECTION
- Carry out the HVAC Module - Dual Automatic Temperature Control (DATC) Cold Boot Process. Alternate Diagnostic Methods - HVAC Module - Dual Automatic Temperature Control
- Carry out the HVAC Module - Dual Automatic Temperature Control (DATC) On-Demand Self-Test. Alternate Diagnostic Methods - HVAC Module - Dual Automatic Temperature Control
- 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.
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