tac 50 error 154

bk2 output wont turn on. replaced output and input models and all associated with bk1,bk2,bk3 on the pmi cards . car runs a little way on auto or inspection and fires me a 154. swapped pmi cards between it and its next door neighbour. brake cards too. im going to the governor encoder next. thanks in advance for any help.

Does the BK1 contactor pick and BK1 input go high? If contactor picks but BK1 doesn’t go high, it’s fed from the K1 relay on Brake Reg. Through BK1 contact but I’m not sure what picks K1. Make sure you have 24v on the brake reg card con1 1-2. And you’re saying the IO never even goes high in IMS right? But the brake does pick and car runs until it realized BK2 is low to the brake regulator card? I’m surprised the brake ever picks at all.

Bk1 picks.bk1 goes high. Bk2 output does not turn on. Everyting else checks out.brake picks. Car runs a few feet. Then error 154.

You got me. One thing that I have had some luck with on situations like this is taking a slo-mo video of the IO map on a running car with one phone, then another on the bad car with a 2nd phone then go through both frame by frame. You may see an input go high right before BK2 does on the working car that isn’t on the problem car. There may be an input needed that we aren’t thinking about.

I found that when it spits out 154 and stops, that im losing bk0 output or drvrdy output before bk1 coil. Im not losing my saf outputs or anything else between those two outputs and my safety string. Both of those modules i replaced already, so im wondering if its a drive issue now.

What is BKN parameter set to?

Bkn=3.

Its definately losing the signal from the regulator card n.o. contact that goes to the bki input, and then stopping motion due to a 154 fault. I swapped reg cards. Disconnected the cap board in front of bkc. the rectifier fuses are good on the reg board. Im down to the igbt on the that works with the reg board. It will run for 3.96 seconds before faulting.

Haha. Brake. Reg board throwing out 289 vdc to brake coil. Ouch. Other guy swappee the reg board. But not the rectifier or igbt part of the brake regulator. Igbt was shorted on one gate. Output volrage too high. Reg card saw this after 4 seconds and opened output of card that goes to bki input. Car stops. Error 154. Brake reg board defective. Bang on.

Good find. I’ve seen similar on a Schindler TXR5.