89 code 51
Posting Guru
Joined: Jan 2002
Posts: 1,346
Likes: 8
From: Baltimore
51 is Engine Coolant Temperature sensor voltage to high.
Greater than 4.6 volts. Which indicates an open circuit.
The computer reference voltage should be around 5 volts on
the Light Green/Yellow wire.
If you unplug the sensor connector, turn the ignition on
you should measure close to 5 volts across the connector
pins.
Wiggle the connector around and verify the voltage doesn't
change.
With the connector disconnected from the ECT sensor use
a ohm meter and measure the resistance of the ECT sensor.
Typical resistance measurements.
58750 ohms @ 50 degrees F.
40500 ohms @ 65 degrees F.
3600 ohms @ 180 degrees F.
1840 ohms @ 220 degrees F.
Disconnect connector plug that goes to the computer
at the firewall under the hood. Verify the ECT
signal wire pin 7 a Light Green/Yellow wire is not
corroded and making good contact.
Verify at the negative battery terminal the two small
ground wires are making good connection at the
negative battery terminal.
If all that checks out, the only thing left is the computer.
If you run the key on engine off or engine running tests
make sure the engine is at normal operating temperature.
Greater than 4.6 volts. Which indicates an open circuit.
The computer reference voltage should be around 5 volts on
the Light Green/Yellow wire.
If you unplug the sensor connector, turn the ignition on
you should measure close to 5 volts across the connector
pins.
Wiggle the connector around and verify the voltage doesn't
change.
With the connector disconnected from the ECT sensor use
a ohm meter and measure the resistance of the ECT sensor.
Typical resistance measurements.
58750 ohms @ 50 degrees F.
40500 ohms @ 65 degrees F.
3600 ohms @ 180 degrees F.
1840 ohms @ 220 degrees F.
Disconnect connector plug that goes to the computer
at the firewall under the hood. Verify the ECT
signal wire pin 7 a Light Green/Yellow wire is not
corroded and making good contact.
Verify at the negative battery terminal the two small
ground wires are making good connection at the
negative battery terminal.
If all that checks out, the only thing left is the computer.
If you run the key on engine off or engine running tests
make sure the engine is at normal operating temperature.
Thread
Thread Starter
Forum
Replies
Last Post
