#Pcmscan solenoid code

Given that everything on the scan tool looked good, countless other vehicles are fixed with a transmission when they act like this.

#Pcmscan solenoid code

This is the first time I had run into this sort of thing causing this code and symptom, and I can see where it would be very easy to assume that the problem was inside the transmission. Several test drives at highway speeds were performed, and the truck showed no TCC slip, and no codes returned. He agreed that it sure sounded like the PCM had a problem so I decided to pull the trigger.ДЄ new PCM was ordered, installed and programmed. I wanted a second opinion, so I relayed all the information to our lead tech, going over everything that had happened up to this point. At this point it sure looked like we may have a failing PCM. It could recognize that the slip was not coming down with the duty cycle going up, and would set the code. What about that PWM solenoid and the signal to it? Again, I went to the PCM, this time commanding the duty cycle while monitoring it with the DMM, there was no signal present ( Figure 4)! The PCM was showing scan data that made it look like everything was operating as it should be, but there was no actual signal coming from the PCM even though it showed otherwise on the data stream. You would think if there were an actual slip, the degree of slip would be affected by the load, or lack thereof. That seemed strange, no load/full duty-cycle was showing as much slip as driving with a load on it. The PCM scan data showed TCC solenoid turning on, and TCC PWM solenoid start to raise the duty-cycle to full, just like on the test drive, but my TCC slip rpm was still high. I have used this strategy before with gear-ratio codes to see if they would reset on the hoist without the weight and load of the vehicle. Next I ran the vehicle on the hoist while watching the TCC data. Checking from the PCM with a DMM I was able to verify that the signal was getting to the on/off solenoid, and that the solenoid was indeed turning on. C2 (red) contained the TCC PWM signal wire on pin 7, which was a brown wire ( Figure 3). I decided to start my testing at the PCM ( figures 2 & 3).Д¬onnector C1 (blue) at the PCM contained the TCC on/off solenoid control on pin 10, which was a tan/black wire. Both the TCC on/off solenoid and the TCC PWM solenoid are located on the valve body on this transmission and would require dropping the pan to access them.

I decided to try to verify that the on/off solenoid was working and being commanded to work.

The PCM is located on the driverвЂ™s side fender well, so it is easily accessible ( Figure 1). I pulled up the wiring diagram and connector views for the PCM.

Could two transmissions have the same failure? Absolutely possible, but sure seemed unlikely. Everything I looked at pointed to a mechanical failure, but I was starting to doubt this with the information I found out about the previous failure, and the same code being present. They get calls from all kinds of shops and can be a great resource for information. I also ran it past the guys in our technical division. I looked around through TSBs and found all the typical failures you see with this code. By now you may have guessed that the previous failure also involved the P1870 code! It was time to look at this issue a little more closely. As we learned more from the customer, it became clear that there was a pattern present. This truck had the transmission replaced not too long before it came into our shop.