Wastegate Solenoid Error - Code 31


Dec 6, 2015
Been trying to track down this code for a bit and I'm stumped. Things I tried:
  • Checked all fuses
  • Tested TCC (from this post)
  • Unplugged TCC
  • Tested WG electrical
State of the Car:
  • 1985 T-Type
  • Vacuum hoses are new
  • Wastegate solenoid venting to atmosphere (T removed from PCV)
  • Vacuum Brakes (previous owner)
I get the code when boost is over 5lbs and cannot boost over 10lbs. I do get a TCC code and the car shifts weird between 3/4 and hesitates to engage the trans from a standstill.

So maybe the TCC is bad but wouldn't unplugging it allow the WG to work properly??

I've read that the brake switch can cause these types of issues, but the Cruise Control disengages fine when the brakes are applied.

Are there any other tests I can try to rule out the Brake Switch?? The car does have a Vacuum Brake Conversion so maybe the installer messed something up.

Here are some photos of the electrical connections on the Driver's Side:


Also a photo of the Fuse Panel

Thanks folks.
Small update. If I hold the brake lightly the wonky 3/4 shifts and Wastegate Code go away, so definitely looks related. But how do I fix it??

Also, even though I don't get a code for the Wastegate I still can't get anymore than 10lbs of boost. Thoughts??
you may have a bad solenoid, or bad wiring, and either of these could have caused the output driver in the ECM to fail.

You need a DVM (voltmeter, multimeter, etc.) and the wiring schematics for the car, you need to chase out the wiring and measure the resistance of the solenoids.

Okay, so pulled fuses until I found the one that ran the WG then checked all sorts of other stuff that ran on the same circuit, this is what I found:
  • Vapor Cannister
  • Left port on the EGR, other side stayed hot
  • Upper Right port on the TCC, Upper Right and Lower Right stayed hot
I also inspected the brake switch as I didn't throw codes when the brake was partially depressed as well as the trans shifted much better. Noticed that the brake pedal didn't always fully retract which left a small amount of the switch not shut.

For the brake pedal I taped a piece of cardboard in front of the switches to see if that would work, didn't see the point of pulling a bunch of stuff a part if the change did nothing.

For the other devices on the circuit I pulled everything but the WG and went for a drive. Warmed up the car and did a pull, still can't hit more than 10lb boost but no code!! Then plugged in the TCC...no code, then the EGR...no code, then the Vapor Cannister...no code!! So initially looks like the brake switch was the culprit, but I had to run the car in 10k mode for logging so maaayyybee that is why no code??

Going to drive the car a bit tomorrow in a variety of conditions to see if a code pops up when in "normal" mode. If things still look good I'll adjust the brake switches correctly. :crosses fingers:
Another Update.

Brake pedal switch fix was definitely the culprit, been on several drives in a variety of conditions and all is good.

Still can't boost over 10lbs though. :( I'll post up a new thread to try to diagnose that issue. Thanks folks.