Code
P0187
GWM
P — Powertrain
- Low Temperature Sensor B
Views:
UK: 16
EN: 18
RU: 24
AI status
Completed
Completed
100%
Causes
- Short to ground in the sensor signal wire
- Open or shorted wiring harness/connector (corrosion, pin pushed out, damaged insulation)
- Faulty Temperature Sensor B (thermistor failed)
- Poor or intermittent connector contact (moisture, dirt)
- Incorrect or incompatible replacement sensor
- Control module (ECU) internal fault (less common)
Symptoms
- Check Engine Light (MIL) illuminated with P0187 stored
- Incorrect temperature reading in scan tool (very low or near ambient when warmed)
- Cold-start enrichment or altered fueling/idle behavior
- Higher than normal fuel consumption or increased smoke (diesel)
- Possible reduced engine performance or limp-home strategy (rare)
What to check
- Read and record stored DTCs and freeze-frame data with a capable scan tool
- Inspect sensor connector and wiring for corrosion, damage, pins pushed out or contamination
- Back-probe the sensor signal with key ON (engine OFF) and observe live voltage/temperature data
- Measure sensor resistance with sensor disconnected and compare to expected behavior as temperature changes
- Perform continuity and short-to-ground checks between sensor connector and ECU
- Wiggle harness while monitoring live data to reproduce intermittent faults
Signal parameters
- Typical sensor signal range: ~0.1–4.9 V depending on temperature (verify OEM spec for exact range)
- NTC thermistor behavior: resistance decreases as temperature increases (verify OEM resistance vs. temperature table)
- Expected idle/operating readings will vary by vehicle—use OEM tables or a live-data scan tool for reference
- No-load short to ground will show near 0 V at signal pin; open circuit may show high or floating voltage
Diagnostic algorithm
- Retrieve freeze-frame data and all related codes. Note conditions when fault set.
- Visually inspect Temperature Sensor B wiring and connector for damage, corrosion, moisture, or loose pins.
- With key ON (engine OFF) back-probe the sensor signal and reference ground; record sensor voltage. Compare to expected values or typical behavior (voltage should change with temperature).
- Disconnect sensor and measure resistance across its terminals at ambient temperature. If possible, measure resistance at two known temperatures (ice water and warm water) to confirm thermistor response.
- Check continuity from the sensor connector pin to the ECU pin and check for short to ground/short to battery using an ohmmeter.
- If wiring and connectors are good, swap with a known-good identical sensor (if available) or temporarily substitute OEM part and re-check signals.
- Repair any damaged wiring or connector faults. Replace the sensor if its resistance/voltage response is out of specification.
- After repair, clear codes, perform relearn procedures if required, and road-test to confirm the fault does not return.
- If wiring, sensor, and connector all check good, consider ECU input circuit testing or replacement as a last resort.
Likely causes
- Wiring rubbed through and shorted to chassis ground
- Corroded or pushed-out connector pin at sensor or ECU
- Failed thermistor inside the sensor producing a low voltage reading
- Aftermarket/incorrect sensor installed with wrong characteristics
- Water ingress causing low-voltage short in connector
Fault status
Status
ECM detected low/abnormally low signal from Temperature Sensor B circuit (possible short to ground, sensor or connector fault).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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