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Home / DTC / B1229 — Fuel temperature sensor 2 circuit low input

B1229 — Fuel temperature sensor 2 circuit low input

Detailed page for trouble code B1229.

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22,491specific
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Code

B1229

ALFA ROMEO B — Body

Fuel temperature sensor 2 circuit low input

Brand: ALFA ROMEO
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Short to ground in the sensor signal wire
  • Open or corroded connector causing low or no signal
  • Failed fuel temperature sensor (internal short or out-of-spec resistance)
  • Damaged or chafed wiring harness
  • ECU input or ground fault

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Stored B1229 trouble code (fuel temperature sensor 2 circuit low)
  • Incorrect fuel metering or fuel trim anomalies
  • Hard cold start or rough idle after cold start (if ECU relies on fuel temperature)
  • Possible limp-home mode or reduced drivability depending on ECU strategy

What to check

  • Read and record freeze frame and live data for fuel temperature sensor 2
  • Visual inspection of sensor, connector and wiring for damage, corrosion, bent pins or water ingress
  • Check for DTC presence in other related circuits (grounds, reference voltages)
  • Measure voltage at the sensor signal pin with key ON (compare to reference and ground)
  • Measure continuity between signal wire and chassis ground (check for unintended short)
  • Measure sensor resistance at ambient and compare to expected resistance/temperature curve if available

Signal parameters

  • Typical sensor signal: 0–5 V (vehicle may use 5 V or 3.3 V reference depending on model)
  • Low input fault usually flagged when signal is below a low-threshold (commonly
  • Sensor is usually an NTC thermistor — resistance decreases or increases with temperature depending on design
  • Expected signal at ambient: moderate voltage (manufacturer-specific), not near 0 V

Diagnostic algorithm

  1. Connect a diagnostic scanner and confirm the B1229 code and any associated codes or freeze-frame data.
  2. Visually inspect Fuel Temperature Sensor 2, its connector and the wiring harness for damage, corrosion, pin push-out, or water ingress. Repair as needed.
  3. With the key OFF, disconnect the sensor connector and inspect terminals for corrosion, bent pins or contamination. Clean or repair connector as required.
  4. With connector disconnected, measure continuity between the sensor signal wire and chassis ground. If near zero ohms, repair short to ground in the harness.
  5. With connector disconnected, measure resistance of the sensor across its terminals. Compare to manufacturer resistance vs temperature chart if available. Replace sensor if resistance is out of range or shorted.
  6. Reconnect connector. With key ON (engine OFF), back-probe the signal wire and measure voltage relative to ground. Verify reference voltage to sensor (if applicable) and ECU ground integrity.
  7. If wiring and sensor check good but signal remains low at ECU input, inspect ECU ground and power rails. Wiggle test wiring while watching live data to reproduce fault.
  8. If wiring and grounds are OK and sensor replacement does not clear the fault, consider ECU input circuit fault and consult manufacturer guidance for ECU testing or replacement.
  9. After repairs, clear codes and perform road/test-cycle or use live data to confirm the sensor signal is stable and the B1229 does not return.

Likely causes

  • Damaged sensor harness rubbed through and shorted to chassis ground
  • Sensor connector corroded or pins pushed back
  • Sensor element failed and is presenting near-zero resistance
  • Poor ECU ground or damaged ECU input circuit

Fault status

⚠️ Status
Fuel temperature sensor 2 circuit low input — ECU detects signal voltage below expected range. Likely causes include sensor failure, short to ground in the wiring, poor connector contact, or ECU input/ground fault.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

P0112 P0113 P0192 P0193 B1220
89

Browse 89 ALFA ROMEO manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

ALFA ROMEO

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Code

B1229

FIAT B — Body

Fuel temperature sensor 2 circuit low input

Brand: FIAT
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Short to ground in the sensor signal wire
  • Open or corroded connector causing low or no signal
  • Failed fuel temperature sensor (internal short or out-of-spec resistance)
  • Damaged or chafed wiring harness
  • ECU input or ground fault

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Stored B1229 trouble code (fuel temperature sensor 2 circuit low)
  • Incorrect fuel metering or fuel trim anomalies
  • Hard cold start or rough idle after cold start (if ECU relies on fuel temperature)
  • Possible limp-home mode or reduced drivability depending on ECU strategy

What to check

  • Read and record freeze frame and live data for fuel temperature sensor 2
  • Visual inspection of sensor, connector and wiring for damage, corrosion, bent pins or water ingress
  • Check for DTC presence in other related circuits (grounds, reference voltages)
  • Measure voltage at the sensor signal pin with key ON (compare to reference and ground)
  • Measure continuity between signal wire and chassis ground (check for unintended short)
  • Measure sensor resistance at ambient and compare to expected resistance/temperature curve if available

Signal parameters

  • Typical sensor signal: 0–5 V (vehicle may use 5 V or 3.3 V reference depending on model)
  • Low input fault usually flagged when signal is below a low-threshold (commonly
  • Sensor is usually an NTC thermistor — resistance decreases or increases with temperature depending on design
  • Expected signal at ambient: moderate voltage (manufacturer-specific), not near 0 V

Diagnostic algorithm

  1. Connect a diagnostic scanner and confirm the B1229 code and any associated codes or freeze-frame data.
  2. Visually inspect Fuel Temperature Sensor 2, its connector and the wiring harness for damage, corrosion, pin push-out, or water ingress. Repair as needed.
  3. With the key OFF, disconnect the sensor connector and inspect terminals for corrosion, bent pins or contamination. Clean or repair connector as required.
  4. With connector disconnected, measure continuity between the sensor signal wire and chassis ground. If near zero ohms, repair short to ground in the harness.
  5. With connector disconnected, measure resistance of the sensor across its terminals. Compare to manufacturer resistance vs temperature chart if available. Replace sensor if resistance is out of range or shorted.
  6. Reconnect connector. With key ON (engine OFF), back-probe the signal wire and measure voltage relative to ground. Verify reference voltage to sensor (if applicable) and ECU ground integrity.
  7. If wiring and sensor check good but signal remains low at ECU input, inspect ECU ground and power rails. Wiggle test wiring while watching live data to reproduce fault.
  8. If wiring and grounds are OK and sensor replacement does not clear the fault, consider ECU input circuit fault and consult manufacturer guidance for ECU testing or replacement.
  9. After repairs, clear codes and perform road/test-cycle or use live data to confirm the sensor signal is stable and the B1229 does not return.

Likely causes

  • Damaged sensor harness rubbed through and shorted to chassis ground
  • Sensor connector corroded or pins pushed back
  • Sensor element failed and is presenting near-zero resistance
  • Poor ECU ground or damaged ECU input circuit

Fault status

⚠️ Status
Fuel temperature sensor 2 circuit low input — ECU detects signal voltage below expected range. Likely causes include sensor failure, short to ground in the wiring, poor connector contact, or ECU input/ground fault.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

P0112 P0113 P0192 P0193 B1220
Repair manuals

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Code

B1229

LAND ROVER B — Body

Left rear seat temperature sensor

Brand: LAND ROVER
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Short to ground in the sensor signal wire
  • Open or corroded connector causing low or no signal
  • Failed fuel temperature sensor (internal short or out-of-spec resistance)
  • Damaged or chafed wiring harness
  • ECU input or ground fault

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Stored B1229 trouble code (fuel temperature sensor 2 circuit low)
  • Incorrect fuel metering or fuel trim anomalies
  • Hard cold start or rough idle after cold start (if ECU relies on fuel temperature)
  • Possible limp-home mode or reduced drivability depending on ECU strategy

What to check

  • Read and record freeze frame and live data for fuel temperature sensor 2
  • Visual inspection of sensor, connector and wiring for damage, corrosion, bent pins or water ingress
  • Check for DTC presence in other related circuits (grounds, reference voltages)
  • Measure voltage at the sensor signal pin with key ON (compare to reference and ground)
  • Measure continuity between signal wire and chassis ground (check for unintended short)
  • Measure sensor resistance at ambient and compare to expected resistance/temperature curve if available

Signal parameters

  • Typical sensor signal: 0–5 V (vehicle may use 5 V or 3.3 V reference depending on model)
  • Low input fault usually flagged when signal is below a low-threshold (commonly
  • Sensor is usually an NTC thermistor — resistance decreases or increases with temperature depending on design
  • Expected signal at ambient: moderate voltage (manufacturer-specific), not near 0 V

Diagnostic algorithm

  1. Connect a diagnostic scanner and confirm the B1229 code and any associated codes or freeze-frame data.
  2. Visually inspect Fuel Temperature Sensor 2, its connector and the wiring harness for damage, corrosion, pin push-out, or water ingress. Repair as needed.
  3. With the key OFF, disconnect the sensor connector and inspect terminals for corrosion, bent pins or contamination. Clean or repair connector as required.
  4. With connector disconnected, measure continuity between the sensor signal wire and chassis ground. If near zero ohms, repair short to ground in the harness.
  5. With connector disconnected, measure resistance of the sensor across its terminals. Compare to manufacturer resistance vs temperature chart if available. Replace sensor if resistance is out of range or shorted.
  6. Reconnect connector. With key ON (engine OFF), back-probe the signal wire and measure voltage relative to ground. Verify reference voltage to sensor (if applicable) and ECU ground integrity.
  7. If wiring and sensor check good but signal remains low at ECU input, inspect ECU ground and power rails. Wiggle test wiring while watching live data to reproduce fault.
  8. If wiring and grounds are OK and sensor replacement does not clear the fault, consider ECU input circuit fault and consult manufacturer guidance for ECU testing or replacement.
  9. After repairs, clear codes and perform road/test-cycle or use live data to confirm the sensor signal is stable and the B1229 does not return.

Likely causes

  • Damaged sensor harness rubbed through and shorted to chassis ground
  • Sensor connector corroded or pins pushed back
  • Sensor element failed and is presenting near-zero resistance
  • Poor ECU ground or damaged ECU input circuit

Fault status

⚠️ Status
Fuel temperature sensor 2 circuit low input — ECU detects signal voltage below expected range. Likely causes include sensor failure, short to ground in the wiring, poor connector contact, or ECU input/ground fault.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

P0112 P0113 P0192 P0193 B1220
320

Browse 320 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

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Code

B1229

MERCEDES-BENZ B — Body

Heater core temperature (B10/1)

Brand: MERCEDES-BENZ
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Short to ground in the sensor signal wire
  • Open or corroded connector causing low or no signal
  • Failed fuel temperature sensor (internal short or out-of-spec resistance)
  • Damaged or chafed wiring harness
  • ECU input or ground fault

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Stored B1229 trouble code (fuel temperature sensor 2 circuit low)
  • Incorrect fuel metering or fuel trim anomalies
  • Hard cold start or rough idle after cold start (if ECU relies on fuel temperature)
  • Possible limp-home mode or reduced drivability depending on ECU strategy

What to check

  • Read and record freeze frame and live data for fuel temperature sensor 2
  • Visual inspection of sensor, connector and wiring for damage, corrosion, bent pins or water ingress
  • Check for DTC presence in other related circuits (grounds, reference voltages)
  • Measure voltage at the sensor signal pin with key ON (compare to reference and ground)
  • Measure continuity between signal wire and chassis ground (check for unintended short)
  • Measure sensor resistance at ambient and compare to expected resistance/temperature curve if available

Signal parameters

  • Typical sensor signal: 0–5 V (vehicle may use 5 V or 3.3 V reference depending on model)
  • Low input fault usually flagged when signal is below a low-threshold (commonly
  • Sensor is usually an NTC thermistor — resistance decreases or increases with temperature depending on design
  • Expected signal at ambient: moderate voltage (manufacturer-specific), not near 0 V

Diagnostic algorithm

  1. Connect a diagnostic scanner and confirm the B1229 code and any associated codes or freeze-frame data.
  2. Visually inspect Fuel Temperature Sensor 2, its connector and the wiring harness for damage, corrosion, pin push-out, or water ingress. Repair as needed.
  3. With the key OFF, disconnect the sensor connector and inspect terminals for corrosion, bent pins or contamination. Clean or repair connector as required.
  4. With connector disconnected, measure continuity between the sensor signal wire and chassis ground. If near zero ohms, repair short to ground in the harness.
  5. With connector disconnected, measure resistance of the sensor across its terminals. Compare to manufacturer resistance vs temperature chart if available. Replace sensor if resistance is out of range or shorted.
  6. Reconnect connector. With key ON (engine OFF), back-probe the signal wire and measure voltage relative to ground. Verify reference voltage to sensor (if applicable) and ECU ground integrity.
  7. If wiring and sensor check good but signal remains low at ECU input, inspect ECU ground and power rails. Wiggle test wiring while watching live data to reproduce fault.
  8. If wiring and grounds are OK and sensor replacement does not clear the fault, consider ECU input circuit fault and consult manufacturer guidance for ECU testing or replacement.
  9. After repairs, clear codes and perform road/test-cycle or use live data to confirm the sensor signal is stable and the B1229 does not return.

Likely causes

  • Damaged sensor harness rubbed through and shorted to chassis ground
  • Sensor connector corroded or pins pushed back
  • Sensor element failed and is presenting near-zero resistance
  • Poor ECU ground or damaged ECU input circuit

Fault status

⚠️ Status
Fuel temperature sensor 2 circuit low input — ECU detects signal voltage below expected range. Likely causes include sensor failure, short to ground in the wiring, poor connector contact, or ECU input/ground fault.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

P0112 P0113 P0192 P0193 B1220
856

Browse 856 MERCEDES-BENZ manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

MERCEDES-BENZ

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+100 karma for a short comment :)
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Code

B1229

Other B — Body

Fuel Temperature Sensor #2 Circuit Short to Ground

Brand: Other
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Short to ground in the sensor signal wire
  • Open or corroded connector causing low or no signal
  • Failed fuel temperature sensor (internal short or out-of-spec resistance)
  • Damaged or chafed wiring harness
  • ECU input or ground fault

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Stored B1229 trouble code (fuel temperature sensor 2 circuit low)
  • Incorrect fuel metering or fuel trim anomalies
  • Hard cold start or rough idle after cold start (if ECU relies on fuel temperature)
  • Possible limp-home mode or reduced drivability depending on ECU strategy

What to check

  • Read and record freeze frame and live data for fuel temperature sensor 2
  • Visual inspection of sensor, connector and wiring for damage, corrosion, bent pins or water ingress
  • Check for DTC presence in other related circuits (grounds, reference voltages)
  • Measure voltage at the sensor signal pin with key ON (compare to reference and ground)
  • Measure continuity between signal wire and chassis ground (check for unintended short)
  • Measure sensor resistance at ambient and compare to expected resistance/temperature curve if available

Signal parameters

  • Typical sensor signal: 0–5 V (vehicle may use 5 V or 3.3 V reference depending on model)
  • Low input fault usually flagged when signal is below a low-threshold (commonly
  • Sensor is usually an NTC thermistor — resistance decreases or increases with temperature depending on design
  • Expected signal at ambient: moderate voltage (manufacturer-specific), not near 0 V

Diagnostic algorithm

  1. Connect a diagnostic scanner and confirm the B1229 code and any associated codes or freeze-frame data.
  2. Visually inspect Fuel Temperature Sensor 2, its connector and the wiring harness for damage, corrosion, pin push-out, or water ingress. Repair as needed.
  3. With the key OFF, disconnect the sensor connector and inspect terminals for corrosion, bent pins or contamination. Clean or repair connector as required.
  4. With connector disconnected, measure continuity between the sensor signal wire and chassis ground. If near zero ohms, repair short to ground in the harness.
  5. With connector disconnected, measure resistance of the sensor across its terminals. Compare to manufacturer resistance vs temperature chart if available. Replace sensor if resistance is out of range or shorted.
  6. Reconnect connector. With key ON (engine OFF), back-probe the signal wire and measure voltage relative to ground. Verify reference voltage to sensor (if applicable) and ECU ground integrity.
  7. If wiring and sensor check good but signal remains low at ECU input, inspect ECU ground and power rails. Wiggle test wiring while watching live data to reproduce fault.
  8. If wiring and grounds are OK and sensor replacement does not clear the fault, consider ECU input circuit fault and consult manufacturer guidance for ECU testing or replacement.
  9. After repairs, clear codes and perform road/test-cycle or use live data to confirm the sensor signal is stable and the B1229 does not return.

Likely causes

  • Damaged sensor harness rubbed through and shorted to chassis ground
  • Sensor connector corroded or pins pushed back
  • Sensor element failed and is presenting near-zero resistance
  • Poor ECU ground or damaged ECU input circuit

Fault status

⚠️ Status
Fuel temperature sensor 2 circuit low input — ECU detects signal voltage below expected range. Likely causes include sensor failure, short to ground in the wiring, poor connector contact, or ECU input/ground fault.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

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P0112 P0113 P0192 P0193 B1220
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