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Home / DTC / B1238 — Overheating

B1238 — Overheating

Detailed page for trouble code B1238.

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22,491specific
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Code

B1238

ALFA ROMEO B — Body

Overheating

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

Causes

  • Low coolant level or coolant loss (leak)
  • Faulty thermostat (stuck closed)
  • Failed water pump or poor coolant circulation
  • Radiator blockage or collapsed/restricted hose
  • Cooling fan(s) not running or fan control failure
  • Faulty engine coolant temperature (ECT) sensor or wiring/connectors

Symptoms

  • Coolant temperature gauge pegged high or rapidly rising
  • Instrument cluster warning lamp or text message for overheating
  • Steam or visible coolant from radiator/overflow
  • Sweet coolant smell in engine bay or on exhaust
  • Loss of engine power, knocking, rough running or misfire when hot
  • Frequent need to add coolant

What to check

  • Read and record freeze‑frame and all stored DTCs with a diagnostic scanner; check pending codes
  • Check coolant level in reservoir and radiator (only when cold) and inspect for visible leaks
  • Visually inspect hoses, radiator, and heater core area for damage or blockage
  • Check radiator cap condition and system pressure with a hand pump pressure tester
  • Start engine and watch cooling fans operate; verify fan control signals with scan tool
  • Monitor live coolant temperature (ECT) with a scan tool while engine warms up; compare to expected rise and thermostat opening behavior

Signal parameters

  • ECT sensor typical operating range at idle: ~20°C (cold) to 90–105°C (normal operating); overheat flagged above normal operating limit (varies by model)
  • ECT sensor: open/short fault indicated by extreme voltage or resistance (e.g., very high voltage or infinite resistance) — confirm with manufacturer specs
  • Cooling fan command: ON/OFF or PWM duty cycle from ECU; verify command value in scanner and actual fan speed
  • Radiator pressure test: system should hold specified pressure (commonly 1.0–1.5 bar) without loss during test period
  • Thermostat opening temperature: compare live data to expected temperature range (check Alfa Romeo spec)
  • Heater inlet/outlet temperature difference: when circulating, hoses should show flow/temperature change

Diagnostic algorithm

  1. Retrieve all DTCs and freeze‑frame data; save live coolant temperature trace while warming from cold.
  2. With engine cold, check coolant level and top up if low; inspect for external leaks, stains, or coolant odor.
  3. Perform a visual inspection of belts, hoses, radiator, and overflow tank; replace damaged components.
  4. Pressure test the cooling system to identify external leaks and check radiator cap holding pressure.
  5. Start engine and monitor coolant temperature rise and fan operation. Verify fans run when commanded by the scanner or when A/C is on.
  6. Test ECT sensor: measure resistance/voltage and compare to manufacturer specification; inspect and repair any wiring/connectors before replacing sensors.
  7. Check thermostat operation: observe temperature at thermostat housing or perform a bypass test if safe; replace thermostat if it fails to open at spec temperature.
  8. Inspect water pump for coolant leakage, bearing noise, or poor flow. Replace if pump failure suspected.
  9. If coolant is contaminated (oil, exhaust gases) or coolant level drops without external leak, perform combustion gas test and consider compression/leakdown test to evaluate head gasket/engine integrity.
  10. After repairs, refill/bleed cooling system properly, clear codes, and conduct a road/run‑up test while monitoring temperatures to confirm fault resolution.

Likely causes

  • Low coolant level or visible external leak
  • Cooling fan(s) inoperative (electrical/fuse/relay/ECU control)
  • Thermostat stuck closed or opening late
  • Faulty ECT sensor giving incorrect high readings
  • Restricted radiator or clogged passages reducing heat exchange
  • Water pump impeller failure or drive belt slip

Fault status

⚠️ Status
Control module detected an overheating condition or over‑temperature signal from the cooling system. Check coolant level, cooling fans, thermostat, ECT sensor and system integrity; further diagnosis required to identify root cause.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-4 hours

Similar codes

P0217 P0128 P0117 P0118 P0125 P0480
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

B1238

FIAT B — Body

Overheating

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

Causes

  • Low coolant level or coolant loss (leak)
  • Faulty thermostat (stuck closed)
  • Failed water pump or poor coolant circulation
  • Radiator blockage or collapsed/restricted hose
  • Cooling fan(s) not running or fan control failure
  • Faulty engine coolant temperature (ECT) sensor or wiring/connectors

Symptoms

  • Coolant temperature gauge pegged high or rapidly rising
  • Instrument cluster warning lamp or text message for overheating
  • Steam or visible coolant from radiator/overflow
  • Sweet coolant smell in engine bay or on exhaust
  • Loss of engine power, knocking, rough running or misfire when hot
  • Frequent need to add coolant

What to check

  • Read and record freeze‑frame and all stored DTCs with a diagnostic scanner; check pending codes
  • Check coolant level in reservoir and radiator (only when cold) and inspect for visible leaks
  • Visually inspect hoses, radiator, and heater core area for damage or blockage
  • Check radiator cap condition and system pressure with a hand pump pressure tester
  • Start engine and watch cooling fans operate; verify fan control signals with scan tool
  • Monitor live coolant temperature (ECT) with a scan tool while engine warms up; compare to expected rise and thermostat opening behavior

Signal parameters

  • ECT sensor typical operating range at idle: ~20°C (cold) to 90–105°C (normal operating); overheat flagged above normal operating limit (varies by model)
  • ECT sensor: open/short fault indicated by extreme voltage or resistance (e.g., very high voltage or infinite resistance) — confirm with manufacturer specs
  • Cooling fan command: ON/OFF or PWM duty cycle from ECU; verify command value in scanner and actual fan speed
  • Radiator pressure test: system should hold specified pressure (commonly 1.0–1.5 bar) without loss during test period
  • Thermostat opening temperature: compare live data to expected temperature range (check Alfa Romeo spec)
  • Heater inlet/outlet temperature difference: when circulating, hoses should show flow/temperature change

Diagnostic algorithm

  1. Retrieve all DTCs and freeze‑frame data; save live coolant temperature trace while warming from cold.
  2. With engine cold, check coolant level and top up if low; inspect for external leaks, stains, or coolant odor.
  3. Perform a visual inspection of belts, hoses, radiator, and overflow tank; replace damaged components.
  4. Pressure test the cooling system to identify external leaks and check radiator cap holding pressure.
  5. Start engine and monitor coolant temperature rise and fan operation. Verify fans run when commanded by the scanner or when A/C is on.
  6. Test ECT sensor: measure resistance/voltage and compare to manufacturer specification; inspect and repair any wiring/connectors before replacing sensors.
  7. Check thermostat operation: observe temperature at thermostat housing or perform a bypass test if safe; replace thermostat if it fails to open at spec temperature.
  8. Inspect water pump for coolant leakage, bearing noise, or poor flow. Replace if pump failure suspected.
  9. If coolant is contaminated (oil, exhaust gases) or coolant level drops without external leak, perform combustion gas test and consider compression/leakdown test to evaluate head gasket/engine integrity.
  10. After repairs, refill/bleed cooling system properly, clear codes, and conduct a road/run‑up test while monitoring temperatures to confirm fault resolution.

Likely causes

  • Low coolant level or visible external leak
  • Cooling fan(s) inoperative (electrical/fuse/relay/ECU control)
  • Thermostat stuck closed or opening late
  • Faulty ECT sensor giving incorrect high readings
  • Restricted radiator or clogged passages reducing heat exchange
  • Water pump impeller failure or drive belt slip

Fault status

⚠️ Status
Control module detected an overheating condition or over‑temperature signal from the cooling system. Check coolant level, cooling fans, thermostat, ECT sensor and system integrity; further diagnosis required to identify root cause.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-4 hours

Similar codes

P0217 P0128 P0117 P0118 P0125 P0480
Repair manuals

Manual library for FIAT

26

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FIAT

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Code

B1238

LAND ROVER B — Body

Overheating

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

Causes

  • Low coolant level or coolant loss (leak)
  • Faulty thermostat (stuck closed)
  • Failed water pump or poor coolant circulation
  • Radiator blockage or collapsed/restricted hose
  • Cooling fan(s) not running or fan control failure
  • Faulty engine coolant temperature (ECT) sensor or wiring/connectors

Symptoms

  • Coolant temperature gauge pegged high or rapidly rising
  • Instrument cluster warning lamp or text message for overheating
  • Steam or visible coolant from radiator/overflow
  • Sweet coolant smell in engine bay or on exhaust
  • Loss of engine power, knocking, rough running or misfire when hot
  • Frequent need to add coolant

What to check

  • Read and record freeze‑frame and all stored DTCs with a diagnostic scanner; check pending codes
  • Check coolant level in reservoir and radiator (only when cold) and inspect for visible leaks
  • Visually inspect hoses, radiator, and heater core area for damage or blockage
  • Check radiator cap condition and system pressure with a hand pump pressure tester
  • Start engine and watch cooling fans operate; verify fan control signals with scan tool
  • Monitor live coolant temperature (ECT) with a scan tool while engine warms up; compare to expected rise and thermostat opening behavior

Signal parameters

  • ECT sensor typical operating range at idle: ~20°C (cold) to 90–105°C (normal operating); overheat flagged above normal operating limit (varies by model)
  • ECT sensor: open/short fault indicated by extreme voltage or resistance (e.g., very high voltage or infinite resistance) — confirm with manufacturer specs
  • Cooling fan command: ON/OFF or PWM duty cycle from ECU; verify command value in scanner and actual fan speed
  • Radiator pressure test: system should hold specified pressure (commonly 1.0–1.5 bar) without loss during test period
  • Thermostat opening temperature: compare live data to expected temperature range (check Alfa Romeo spec)
  • Heater inlet/outlet temperature difference: when circulating, hoses should show flow/temperature change

Diagnostic algorithm

  1. Retrieve all DTCs and freeze‑frame data; save live coolant temperature trace while warming from cold.
  2. With engine cold, check coolant level and top up if low; inspect for external leaks, stains, or coolant odor.
  3. Perform a visual inspection of belts, hoses, radiator, and overflow tank; replace damaged components.
  4. Pressure test the cooling system to identify external leaks and check radiator cap holding pressure.
  5. Start engine and monitor coolant temperature rise and fan operation. Verify fans run when commanded by the scanner or when A/C is on.
  6. Test ECT sensor: measure resistance/voltage and compare to manufacturer specification; inspect and repair any wiring/connectors before replacing sensors.
  7. Check thermostat operation: observe temperature at thermostat housing or perform a bypass test if safe; replace thermostat if it fails to open at spec temperature.
  8. Inspect water pump for coolant leakage, bearing noise, or poor flow. Replace if pump failure suspected.
  9. If coolant is contaminated (oil, exhaust gases) or coolant level drops without external leak, perform combustion gas test and consider compression/leakdown test to evaluate head gasket/engine integrity.
  10. After repairs, refill/bleed cooling system properly, clear codes, and conduct a road/run‑up test while monitoring temperatures to confirm fault resolution.

Likely causes

  • Low coolant level or visible external leak
  • Cooling fan(s) inoperative (electrical/fuse/relay/ECU control)
  • Thermostat stuck closed or opening late
  • Faulty ECT sensor giving incorrect high readings
  • Restricted radiator or clogged passages reducing heat exchange
  • Water pump impeller failure or drive belt slip

Fault status

⚠️ Status
Control module detected an overheating condition or over‑temperature signal from the cooling system. Check coolant level, cooling fans, thermostat, ECT sensor and system integrity; further diagnosis required to identify root cause.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-4 hours

Similar codes

P0217 P0128 P0117 P0118 P0125 P0480
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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+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
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Code

B1238

Other B — Body

Over Temperature Fault

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

Causes

  • Low coolant level or coolant loss (leak)
  • Faulty thermostat (stuck closed)
  • Failed water pump or poor coolant circulation
  • Radiator blockage or collapsed/restricted hose
  • Cooling fan(s) not running or fan control failure
  • Faulty engine coolant temperature (ECT) sensor or wiring/connectors

Symptoms

  • Coolant temperature gauge pegged high or rapidly rising
  • Instrument cluster warning lamp or text message for overheating
  • Steam or visible coolant from radiator/overflow
  • Sweet coolant smell in engine bay or on exhaust
  • Loss of engine power, knocking, rough running or misfire when hot
  • Frequent need to add coolant

What to check

  • Read and record freeze‑frame and all stored DTCs with a diagnostic scanner; check pending codes
  • Check coolant level in reservoir and radiator (only when cold) and inspect for visible leaks
  • Visually inspect hoses, radiator, and heater core area for damage or blockage
  • Check radiator cap condition and system pressure with a hand pump pressure tester
  • Start engine and watch cooling fans operate; verify fan control signals with scan tool
  • Monitor live coolant temperature (ECT) with a scan tool while engine warms up; compare to expected rise and thermostat opening behavior

Signal parameters

  • ECT sensor typical operating range at idle: ~20°C (cold) to 90–105°C (normal operating); overheat flagged above normal operating limit (varies by model)
  • ECT sensor: open/short fault indicated by extreme voltage or resistance (e.g., very high voltage or infinite resistance) — confirm with manufacturer specs
  • Cooling fan command: ON/OFF or PWM duty cycle from ECU; verify command value in scanner and actual fan speed
  • Radiator pressure test: system should hold specified pressure (commonly 1.0–1.5 bar) without loss during test period
  • Thermostat opening temperature: compare live data to expected temperature range (check Alfa Romeo spec)
  • Heater inlet/outlet temperature difference: when circulating, hoses should show flow/temperature change

Diagnostic algorithm

  1. Retrieve all DTCs and freeze‑frame data; save live coolant temperature trace while warming from cold.
  2. With engine cold, check coolant level and top up if low; inspect for external leaks, stains, or coolant odor.
  3. Perform a visual inspection of belts, hoses, radiator, and overflow tank; replace damaged components.
  4. Pressure test the cooling system to identify external leaks and check radiator cap holding pressure.
  5. Start engine and monitor coolant temperature rise and fan operation. Verify fans run when commanded by the scanner or when A/C is on.
  6. Test ECT sensor: measure resistance/voltage and compare to manufacturer specification; inspect and repair any wiring/connectors before replacing sensors.
  7. Check thermostat operation: observe temperature at thermostat housing or perform a bypass test if safe; replace thermostat if it fails to open at spec temperature.
  8. Inspect water pump for coolant leakage, bearing noise, or poor flow. Replace if pump failure suspected.
  9. If coolant is contaminated (oil, exhaust gases) or coolant level drops without external leak, perform combustion gas test and consider compression/leakdown test to evaluate head gasket/engine integrity.
  10. After repairs, refill/bleed cooling system properly, clear codes, and conduct a road/run‑up test while monitoring temperatures to confirm fault resolution.

Likely causes

  • Low coolant level or visible external leak
  • Cooling fan(s) inoperative (electrical/fuse/relay/ECU control)
  • Thermostat stuck closed or opening late
  • Faulty ECT sensor giving incorrect high readings
  • Restricted radiator or clogged passages reducing heat exchange
  • Water pump impeller failure or drive belt slip

Fault status

⚠️ Status
Control module detected an overheating condition or over‑temperature signal from the cooling system. Check coolant level, cooling fans, thermostat, ECT sensor and system integrity; further diagnosis required to identify root cause.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-4 hours

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P0217 P0128 P0117 P0118 P0125 P0480
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