Error Codes 15 and 44

[SWeaver724]

Hello! I have a 1995 GMC Safari that I’m a little puzzled with, when I first start the van it runs well with no code but after driving for about 15 minutes it will throw on the service engine light and it gives me the codes 15 and 44! When the light comes on it will start idling oddly and and on occasion stall other times the light will go away and it will run well for another random period of time! Any suggestions on what could possibly be wrong??? I recently had the water pump, coolant temp sensor, and pretty much all my lines (brake, gas, trans etc.) replaces!

[Leeann_93]

Coolant temp sensor - for the ECM, not the gauge - was replaced? Are you sure the correct sensor was replaced? There are two: one for the gauge, one for the computer.

44 means O2 sensor is reporting a lean condition, which can be caused by the ECM not receiving correct information on engine coolant temp. It also can mean the wiring to the oxygen sensor is damaged or not making good connection with the sensor. The 15 also can mean that the wiring to the CTS is damaged or disconnected.

[SWeaver724]

I changed the coolant temp sensor on the front of the engine, the one next to the upper radiator hose! I may try to change it again since it is under warranty still

[SWeaver724]

It’s just odd that it only does it after it’s heated up if I’m on the highway it’s fine but as soon as I slow down or stop it starts acting up!

[Leeann_93]

Moved to Engines

[Big_kid]

The sensor you changed IS the one for the computer. The one in the driver side head is for the gauge.

I would chase down the 15 first. If the computer sees a temperature reading warmer than the actual temperature, it would cause a lean condition. There should be a ground wire very close to/on the thermostat housing and coolant temperature sensor. Make sure it was reinstalled, and is clean. Take a meter to the ground wire while moving it around to make sure it isn't broken/intermittent. You can do the same to the wires going to the computer. It is located behind the front passenger kick panel. A year ago I knew the pin numbers and which plug off the top of my head. A quick poke on the autozone website shows Black and yellow, pins B3 (black) and B8 (yellow) per the autozone website wiring diagram:
https://www.autozone.com/repairinfo/rep ... 52800a824a



Lifted from another forum I found when I was battling my code 15 after my swap:

https://www.chevytalk.org/fusionbb/show ... tid/176155

15 - Coolant Sensor Circuit - Excessive Low temperature indicated

To test the coolant sensor, unplug the wire connector and test the resistance across the two terminals of the SENSOR with an ohm meter.

The sensor screws into the intake manifold, on the front passenger side, by the thermostat housing.

Coolant sensor approximate resistance specifications:
177 ohms @ 212 deg. F. or 100 deg. C.
241 ohms @ 194 deg. F. or 90 deg. C.
332 ohms @ 176 deg. F. or 80 deg. C.
467 ohms @ 158 deg. F. or 70 deg. C.
667 ohms @ 140 deg. F. or 60 deg. C.
973 ohms @ 122 deg. F. or 50 deg. C.
1188 ohms @ 113 deg. F. or45 deg. C.
1459 ohms @ 104 deg. F. or 40 deg. C.
1802 ohms @ 95 deg. F. or 35 deg. C.
2238 ohms @ 86 deg. F. or 30 deg. C.
2796 ohms @ 77 deg. F. or 25 deg. C.
3520 ohms @ 68 deg. F. or 20 deg. C.
4450 ohms @ 59 deg. F. or 15 deg. C.
5670 ohms @ 50 deg. F. or 10 deg. C.
7280 ohms @ 41 deg. F. or 5 deg. C.
9420 ohms @ 32 deg. F. or 0 deg. C.
12300 ohms @ 23 deg. F. or -5 deg. C.
16180 ohms @ 14 deg. F. or -10 deg. C.
21450 ohms @ 5 deg. F. or -15 deg. C.
28680 ohms @ -4 deg. F. or -20 deg. C.
52700 ohms @ -22 deg. F. or -30 deg. C.
100700 ohms @ -40 deg. F. or - 40 deg. C.


Let us know what you find.

[dramey]

When my engine coolant sensor went bad, I found it using my scan tool. The engine coolant sensor was telling the computer that the coolant was -40F when the outside air temperature was in the 60’s or 70’s.