B1252

Code

FIAT B — Body

Interior air temperature sensor short to positive

Brand: FIAT

Type: B — Body

Views: UK: 5 EN: 6 RU: 6

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged sensor (internal short to positive supply)
Shorted wiring or chafed insulation contacting a positive feed
Faulty or corroded connector making unintended contact with battery/ignition positive
Water ingress or contamination at sensor/connector
Faulty climate control / body control module (less common)

Symptoms

Stored B1252 in body/climate control module
Incorrect or extreme interior temperature reading on HVAC display
Automatic climate control not maintaining set temperature
Inconsistent HVAC behavior or poor cabin temperature regulation
Possible related HVAC fault messages or limp mode of climate functions

What to check

Read stored freeze-frame and live data from body/climate control module with a scan tool
Inspect sensor location and connector for damage, corrosion or water
Visually inspect wiring harness for chafing, pinches, repairs, or rodent damage along the route
With ignition ON, measure sensor signal voltage at the connector and compare to expected range
Measure sensor resistance (with sensor disconnected) across its terminals at ambient temperature and verify correct thermistor behavior
Check for continuity/short from the sensor signal wire to battery positive and to ground

Signal parameters

Typical sensor type: NTC thermistor (resistance decreases as temperature rises)
Expected voltage at sensor circuit with ignition ON and sensor connected: commonly ~0.3–4.5 V depending on temperature and vehicle (varies by design)
Expected resistance at ~20–25°C: commonly in the kilo-ohm range (e.g., ~2k–12kΩ depending on sensor spec) — consult OEM spec for exact values
Fault indication for this code: signal voltage near battery/ignition positive or above module's allowed threshold
When disconnected: if signal wire measures near battery positive with ignition ON, there is a short to positive in wiring or at the module

Diagnostic algorithm

Connect scan tool, confirm B1252 and record freeze-frame/live data for interior air temperature sensor reading and related parameters.
Visually inspect the sensor and connector (usually in the dash/evaporator housing). Look for corrosion, water, pin damage, or evidence of shorting.
With ignition OFF, disconnect the sensor connector. Inspect pins for corrosion, bent pins, or foreign material. Repair or clean as needed.
With ignition ON (accessory), measure voltage at the sensor connector terminal (backprobe at module/sensor harness): - If terminal reads near battery positive, there is a short to positive in wiring or module. Trace wiring toward module to find damage. - If terminal reads within expected reference range (not high), proceed to step 5.
Measure sensor resistance at ambient temperature with sensor removed. Verify resistance matches expected thermistor behavior (resistance should change with temperature). If sensor shows short to positive internally (very low resistance to positive) or open, replace sensor.
Check continuity between the signal wire and battery positive with ignition OFF. If continuity present (short), isolate section of harness and repair (splice, replace harness section).
If wiring and sensor check OK, backprobe module input pin and check for correct reference/pull-up behavior per OEM; if the input is tied to positive at the module, suspect module fault and consult manufacturer repair procedures.
After repairs, clear codes and test by cycling ignition and operating climate system; verify sensor readings and that B1252 does not return.

Likely causes

Wiring harness short to positive between sensor and module (most likely)
Failed/intermittent interior air temperature sensor element
Connector corrosion or pin pushed into contact with a positive circuit
Module input driver fault (if wiring and sensor check OK)

Fault status

⚠️ Status

Interior air temperature sensor circuit — short to positive voltage detected by body/climate control module. Module flagged fault when sensor signal exceeds allowable high threshold.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-1.5 hours

Similar codes

Your experience will help others

+100 karma for a short comment :)

Was this AI description helpful?

Your feedback helps improve AI descriptions.

👍 Like 0 👎 Dislike 0

Send to email