1989 GMC C2500 V8 Two Wheel Drive Automatic
I keep getting error codes 15 (low value of coolant temperature sensor), 24 (lean O2 sensor) and 44 (vehicle speed sensor) simultaneously, even after clearing the codes. I just need to drive 2 or 3 minutes, the Check engine light turns on, and the Actron OBDC scanner shows errors 15, 24 and 44 again.
I checked the voltage (5V) and resistor value (300 Ohms when hot) of the coolant temperature sensor, this is OK.
I checked the voltage on the single wire O2 sensor, and got 400mV when the engine is cold, and 100mV when it's hot. This looks normal as well according to a repair manual.
I didn't checked the vehicle speed sensor, but I can't see anything wrong on the speedometer while driving.
The ECM runs all the time in open loop.
One error code, OK, I could understand, but why the three of them? How to solve this problem?
Check your battery to make sure it is in good shape. A poor battery can cause this. Also check the coolant sensor wire to see if the sensor has leaked antifreeze up the wire. That may have happened. Check al l the sensors for power to them and out. Alot of times it's just a poor connection.