Pinpoint Test A: DTC B1251 Or DTC B1253 - Air Temperature Internal Sensor Circuit Open Or Short To Ground
Climate Control System
Pinpoint Tests
Pinpoint Test A: DTC B1251 or DTC B1253 - Air Temperature Internal Sensor Circuit Open or Short to Ground
Refer to Wiring Diagram Set 55 (Escape/Mariner, Escape Hybrid/Mariner Hybrid), Automatic Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, the in-vehicle air temperature sensor receives ground from the HVAC module through circuit RH111 (GY/BU). A 5-volt reference voltage is supplied to the in-vehicle air temperature sensor from the HVAC module 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
PINPOINT TEST A: DTC B1251 OR DTC B1253 - AIR TEMPERATURE INTERNAL SENSOR CIRCUIT OPEN OR SHORT TO GROUND
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A1 CHECK THE SENSOR RESISTANCE
- Ignition OFF.
- Disconnect: In-Vehicle Temperature Sensor C2247.
- Measure the resistance between in-vehicle temperature sensor C2247 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 A2.
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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A2 CHECK THE HVAC SENSOR OUTPUT VOLTAGE
- Ignition ON.
- Press the AUTO button.
- Measure the voltage between in-vehicle temperature sensor C2247-1, circuit VH414 (GN/BU), harness side and C2247-3, circuit RH111 (GY/BU), harness side.
- Is the voltage between 4.7 and 5.1 volts?
Yes
INSTALL a new in-vehicle temperature sensor. If code returns, GO to A7.
No
If diagnosing DTC B1251, GO to A3.
If diagnosing DTC B1253, GO to A5.
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A3 CHECK CIRCUIT VH414 (GN/BU) FOR AN OPEN
- Ignition OFF.
- Disconnect: HVAC Module C2356a.
- Measure the resistance between HVAC module C2356b-23, circuit VH414 (GN/BU), harness side and in-vehicle temperature sensor C2247-1, circuit VH414 (GN/BU), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to A4.
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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A4 CHECK CIRCUIT RH111 (GY/BU) FOR AN OPEN
- Measure the resistance between HVAC module C2356a-10, circuit RH111 (GY/BU), harness side and in-vehicle temperature sensor C2247-3, circuit RH111 (GY/BU), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to A7.
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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A5 CHECK CIRCUIT VH414 (GN/BU) FOR A SHORT TO CIRCUIT RH111 (GY/BU)
- Ignition OFF.
- Disconnect: HVAC Module C2356a.
- Measure the resistance between in-vehicle temperature sensor C2247-1, circuit VH414 (GN/BU), harness side and C2247-3, circuit RH111 (GY/BU), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to A6.
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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A6 CHECK CIRCUIT VH414 (GN/BU) FOR A SHORT TO GROUND
- Measure the resistance between HVAC module C2356b-23, circuit VH414 (GN/BU), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to A7.
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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A7 CHECK THE 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 - Diagnostic Methods
- 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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