Hey All,

I'm having trouble with the 4WD on a 1999 S10 blazer LT. I replaced the radiator and the next day, when I started it up the selector switch lights were out and the 4 wheel service light came on. Its currently in 2hi and pushing the selector switch buttons doesn't do a thing. I had the trouble codes read and C0315 "motor ground circuit open" popped up. I checked the 4WD, ATC, and crack fuses, all tested fine.

I'm hoping you guys have some ideas, because I'm pretty stuck.

Thanks

 

The problem is just as the C0315 says: "motor ground circuit open". The "motor" is the encoder motor on the transfer case, there is an open circuit, (broken wire) somewhere. We need to know if you have the NP1 NV233 2 speed selectable transfer case, (3 button switch on the dash). Or the NP8 NV236 2 speed automatic transfer case, (4 button switch on the dash).

 

We had several inches of snow a few days ago so I had to switch to 4 wd to get around. I have a 1994 Chevy Blazer with the hi or lo switch on the dash. Now the car keeps going into 4 wd on it's own and I can't get it to switch off of it. I was able to turn it off last night when I parked but when I went out and started it this morning it was back in 4 wd and I couldn't get it out. I have already been told because of frame rust it won't pass inspection in March. I'm on a fixed income and really can't afford to get it fixed. Anybody know what could be causing this and how much it would cost to fix it. Is it worth it or should I just try to trade it in?

Ron

 

Captain Hook,

Thanks for the response, I appreciate the help. I have the NP8 NV236 2 speed automatic transfer case, (4 button switch on the dash). In doing so research on the alldata database at the library, I was able to determine exactly what you said. That the only cause is a break in conductivity. Is there any common places that this occurs in these cars?

thanks again

 

At the TCCM, (Transfer Case Control Module) located behind the right side kick panel: Connector C2 has 4 wires. Terminal "A" has a black wire and terminal "B" has a red wire. Those 2 wires go directly to the shift motor inside the encoder, (left side of transfer case). Unplug the TCCM connector C2, and the encoder connector, and check resistance of both wires, end to end, and post your results.

 

Its been awhile due to the Christmas holiday, but I finally got a chance to test those wires. Both have a resistance of 1.

Also on Alldata, I found a trouble shooting flowchart for the my code. According to that if the ground, terminal C, on the C2 connector has a resistance of less than .5 ohms then the TCCM needs to be replaced. Does that sound correct? I measured the the on my blazer and it is .02 ohms all the way back to the negative side of the battery. I'd really hate to replace such an expensive part if its not the problem, but the flowchart pretty clear.

 

Terminal C in connector C2, (black wire) goes to ground. Resistance must be less than 5 ohms to ground. This is where the TCCM gets the ground to send to the shift motor through C2 terminal A or B, depending on which direction the motor is commanded to rotate. Positive voltage is applied to the other terminal.

With the encoder plugged in, unplug the TCCM Connector 2. Check resistance in the vehicle harness C2, terminal "A" to "B" and post the results.

 

A to B measures 1.5 ohms

 

From the tests we've done here, we found out that both wires going to the shift motor are good, the motor itself is not open, and the ground for the TCCM is good. That pretty much tells us the open ground that the C0315 indicated, is inside the TCCM.

 

Captain Hook,

Thank you for all your help, I really appreciate it. I'll give a new TCCM a try. Hope you had a wonderful holiday.

Thanks again