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Code P0236, Vacuum pump, pulley, sensor, vacuum line


Well-Known Member
Lake Forest, CA
On my way to Moab I lost turbo boost as we were beginning to climb on I-70. I quickly got a pending code P0236 and then that became a stored code P0236. I tried clearing the code with my scangauge and I tried disconnecting the batteries. Both "fixes" worked for a few minutes and then the code would come back.

I made it to Moab (going uphill without Turbo in a 9000+ pound truck that's supposed to have Turbo is... uhm... it builds character) and started researching the code and possible causes. I quickly found info online that told me that it most likely would be the turbo wastegate actuator solenoid. I was about to have a new solenoid shipped in when Dave suggested we take a look at the vacuum pump itself and I'm glad we did: The pump was completely seized up, the pulley was jammed against the pump and the shaft was at an angle it's not supposed to be at. The pump & pulley couldn't turn AT ALL so my serpentine belt was sliding over the pulley and had gotten very shiny on the smooth side.

I got a new vacuum pump and a new pulley and a special tool to press on the pulley (thanks to Mike at Tustin Hummer for shipping out parts so fast) and installed it all along with a new belt and a new tensioner pulley that I had with me (with the help of Matt & Dave)

At this point it was now safe to run the engine again without the risk of a sudden failure of the belt but I still had no turbo boost.

The next day I started looking at the vacuum system. I started by making sure there was a good strong vacuum coming off the pump and in to the solenoid. I also pulled the solenoid and checked to see if it was clogged by dirt and gunk but it wasn't. I traced the vacuum all the way and found that there was plenty of vacuum to operate the water valve for the HVAC. That was all well and good but I couldn't understand how come the vacuum line seemed to end at the water valve. There was supposed to be a vacuum line going to the waste gate.... but there wasn't....

Wait, what? No vacuum line going to the wastegate from the solenoid? and Mike from Tustin Hummer was insisting that there is supposed to be one..... Well there's your problem! A bit more poking around in the valley of the engine and I found that the vacuum line from the solenoid to the wastegate had broken clean off. Quick fix: Add some new vacuum line to connect the two ends and BINGO: Turbo boost!

I can't imagine that the line breaking off the solenoid had ANY relation to the vacuum pump seizing up, that's got to be coincidental.

Ultimately, things are back in working order for the trip home and that's a very good thing.

I have learned a lot about how my truck works on this trip and wrenched more on it than I ever have.

Now I'm off to to re-check the bolts for the vacuum pump and the tensioner pulley as well as the vacuum line and then we are hitting the road back to CA tomorrow.


Super Moderator
Staff member
Central Texas
Always good to know your truck is right before you begin that 750 miles return trip with 4 7000' summits, a 6000' summit and numerous 4000+' summits. :)