Coolant temperature sender
Coolant temperature sender refers to the engine-mounted sender used for the Pontiac Fiero dashboard Temperature gauge and temperature warning-light circuit.
The coolant temperature sender should not be confused with the Coolant temperature sensor used by the ECM.
Overview
The Fiero uses separate temperature-related parts for different purposes.
The coolant temperature sender provides information to the instrument cluster.
The ECM coolant temperature sensor provides information to the ECM.
This distinction is important because a problem with the dashboard gauge does not automatically mean the ECM is receiving incorrect coolant temperature information, and an ECM coolant-temperature trouble code does not automatically mean the dashboard gauge sender is faulty.
Location
Image wanted: Photo or diagram showing the coolant temperature sender location. Ideally include both the 2.8L V6 and 2.5L four-cylinder sender locations, and show how it differs from the ECM coolant temperature sensor.
The coolant temperature sender is mounted on the engine.
The exact location depends on engine and year.
On the 2.8L V6, the coolant temperature sender is separate from the ECM coolant temperature sensor. The ECM sensor is located below the thermostat housing, while the gauge sender is mounted elsewhere on the engine.
On the 2.5L four-cylinder, the sender location may vary by year and engine configuration.
Function
The coolant temperature sender is used by the dashboard temperature gauge and related warning-light circuit.
It is part of the instrument-cluster system, not the ECM fuel-control system.
Related topics:
Sender versus sensor
The coolant temperature sender and coolant temperature sensor are separate parts.
The coolant temperature sender is used by:
- Dashboard temperature gauge
- Temperature warning light, depending on year and circuit
The coolant temperature sensor is used by:
- ECM
- Fuel mixture calculations
- Idle and warm-up behavior
- Closed-loop decisions
- Diagnostic trouble codes such as Code 14 and Code 15
Common symptoms
Possible coolant-temperature-sender or gauge-circuit symptoms include:
- Temperature gauge does not move
- Temperature gauge reads too high
- Temperature gauge reads too low
- Temperature gauge behaves erratically
- Temperature warning light problem
- Gauge needle pegs or moves incorrectly
- Intermittent gauge operation
Diagnosis
Basic diagnostic checks include:
- Determine whether the engine is actually overheating.
- Inspect the coolant temperature sender connector.
- Inspect sender wiring.
- Check for corrosion or poor connector contact.
- Check instrument cluster operation.
- Check related grounds.
- Compare the dashboard gauge with ECM coolant temperature data through ALDL diagnostics if available.
- Check the cooling system if actual overheating is suspected.
Relationship to overheating
A high gauge reading may indicate actual overheating, but the gauge circuit should not be the only source of diagnosis.
If overheating is suspected, the cooling system should be checked directly.
Related topics:
Gauge pegging
Some Fieros are known for temperature-gauge needle pegging during start-up due to wiring or circuit behavior.
If the gauge needle is stuck, mispositioned, or reads incorrectly, inspect the sender circuit, wiring, and instrument cluster.
Related topics:
Notes
Do not replace the ECM coolant temperature sensor when the problem is only with the dashboard temperature gauge.
Do not replace the gauge sender when the problem is an ECM coolant-temperature trouble code.
Correct diagnosis depends on knowing which temperature-related part is being tested.