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Fiat Punto (176) Factory Service Manual (1993-1999)02 · 10 Engine
02 · Engine

Coolant temperature sensor

Make
Fiat
Model
Punto (176) Factory Service Manual
Year
1993–1999
Section
Fuel system (1581) › Coolant temperature sensor
10 EngineCoolant temperature sensor · page 1 of 2

COOLANT TEMPERATURE SENSOR

The sensor is fitted with its sensitive part in contact with the coolant. It provides the ECU with a voltage that varies according to engine temperature in order to correct air output information.

When a signal is received by the sensor, the ECU lengthens fuel injection time to ensure the enrichment necessary for compensating for fuel loss due to the condensation of fuel particles in the inlet ducts while the engine is warming up.

This sensor therefore ensures safe engine operation in the stage following start-up by enriching the mixture. Intensity and duration of enrichment depend on coolant temperature; this facility also allows the engine to work properly during acceleration with the engine cold.

RPM AND TDC SENSOR

The phonic wheel consists of 58 teeth plus a space equivalent to the bulk occupied by two suppressed teeth.

The reference defined by the space occupied by the two missing teeth is used as a basis for measuring the synchronism point (TDC). The synchronism point is delimited by tooth (6). When this passes beneath the sensor, the crankshaft is located with piston pair 1-4 at 14° before TDC. This signal is used by the ECU to compute the ignition advance angles.

Table titled TYPICAL CURVE (rest points) showing resistance values in Ohms corresponding to temperatures from -40°C to 150°C, alongside a diagram of the coolant temperature sensor.
TYPICAL CURVE
(rest points)
°CΩ
- 40100707.0
- 3052684.6
- 2028677.4
- 1016176.9
09423.1
105671.8
203515.4
302237.6
401459.2
50972.8
60667.2
70466.7
80332.3
90240.6
100177.0
110131.9
12099.9
12294.6
12489.7
12685.1
12880.8
13076.8
14059.8
15047.2
Diagram of the RPM and TDC sensor assembly showing the phonic wheel, sensor, sensor mount, and reference notches.
  1. Sensor
  2. Phonic wheel
  3. Sensor mount
  4. TDC reference notch on phonic wheel
  5. TDC reference notch on sensor mount
  6. Synchronism tooth

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