Frequently Asked Question

Cause: This is the minimum value the EIS will display for fluid temperature inputs. It will read this whenever there is

1. An open circuit in the fluid temperature sensing circuit (the wire from the EIS to the sensor), or
2. If an “S” type sensor is used with a “V” type instrument.
3. The sensor is failed.
4. If the ambient temperature is below 65 degrees F

Troubleshooting

1. Checking for an open in the fluid temperature sensing circuit.

Troubleshooting without a voltmeter: Turn on the EIS. Locate the connection connection between the EIS and the temperature probe. Short this connection to ground. (It is not necessary to disconnect the fluid temperature probe for this test, but it is ok to do so if you wish.) The EIS should read a very high value (above 300 F). If the reading does not change, the connection to the EIS is open, or this is not the correct into input to the EIS (wrong wire). An open may be at the d-sub connector, or the wire to the EIS may be broken.

If the EIS does show above 300F in this test, then the ground to the sensor may be open.

Troubleshooting using a voltmeter: To determine if the connection to the EIS is good, turn on the EIS, and with the fluid temperature probe connected, measure voltage on the wire that goes to the EIS. This voltage should be less than 4.85V, and greater than 1.0V, depending on the temperature of the sensor. If this voltage is zero, the connection to the EIS is open. If the voltage is above 4.85V, the ground to the sensor is open.

2. Checking the sensor and instrument type. (See the background section for the oil temperature / coolant temperature section above.)

3. Checking for a bad oil / coolant temperature sensor. An ohmmeter can be used to test the sensor. At room temperature an “S” type sensor will read 5k-15k (5,000 – 15,000) ohms. A VDO type will read 800-1300 ohms.

Troubleshooting without a voltmeter: Turn on the EIS. Locate the connection connection between the EIS and the temperature probe. Short this connection to ground. (It is not necessary to disconnect the fluid temperature probe for this test, but it is ok to do so if you wish.) The EIS should read a very high value (above 300 F). If the reading does not change, the connection to the EIS is open, or this is not the correct into input to the EIS (wrong wire). An open may be at the d-sub connector, or the wire to the EIS may be broken.

If the EIS does show above 300F in this test, then the ground to the sensor may be open.

Troubleshooting using a voltmeter: To determine if the connection to the EIS is good, turn on the EIS, and with the fluid temperature probe connected, measure voltage on the wire that goes to the EIS. This voltage should be less than 4.85V, and greater than 1.0V, depending on the temperature of the sensor. If this voltage is zero, the connection to the EIS is open. If the voltage is above 4.85V, the ground to the sensor is open.