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ECM Code 15


Jan 13, 2002
kirkland, wa
1981 Black
Check engine light is on,
I changed the coolant sensor with a NAPA sensor, cleared the code (disconnected the battery), the check engine light came back on.

I checked ohm on the the sensor it's reading 250-300 hot 5.80 K cold, I was told that the range should be 1k & 100K.
I bought a sensor from the chevy dealer, it's reading about the same as the NAPA sensor (250-300 hot 5.80 cold).

I checked continuity from the sensor to the ECM, it seems to check out fine.

Any ideas what could be causing this problem?
To clear the fault memory.....turn the key switch off and remove the 20 amp fuse located next to the battery for 10 seconds. You can also remove the positve battery cable instead, if you so choose. Until you perform one of these procedures the fault code will remain.
How many pins on the sensor?

What did it look like? and where was it?

it's located at the top on the front of the engine on the intake manifold.

It's round with two wires coming out of it, the original had yellow and black wire coming out of it.
Code 15 requires the engine to run at least 5 minutes before it will clear.

Code 15 = Open coolant sensor circuit
To Test this circuit:
  • Short the Test Terminal (lug "D") to ground (lug "E")
  • Connect a dwell meter to the Mixture Control Solenoid (located on the carb) SET the Dwell for 6 cylinder.
  • Run the engine at partial throttle for at least 1 minute!
  • With the engine at idle, note dwell, Remove the connection from the coolant sensor and jumper the connection together.

IF THE DWELL changes over 5 degrees from when the sensor was connected.. Indicates a sensor is OK.

IF THE DWELL doesn't change.. then:
  • OHM (check resistance of the Sensor) the sensor should read under 1,000 (1k) ohms
  • Sensor reads OVER 1k Ohms then>
  • Sensor is bad and REPLACE IT!

If the Resistance reads under 1K ohms, clean and check connections. Next check for an open in the wiring back to the terminal pins 3 and 7 at the ECM.

Good Luck..

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