2011 Yukon Hybrid randomly shuts off with "SERVICE POWER STEERING"

I accidentally ran my 12V battery dead three weeks ago. After recharging it with my trusty Craftsman battery charger it randomly decides to either not start or it will start and shut off with the message "SERVICE POWER STEERING". When it doesn't start I get two DTC codes:
P0700 - trans ctrl sys error
P2534 - ignition switch run/start position circuit low

These don't seem related. It was very intermittent at first, but now it's getting more frequent. I'm afraid the charge/jump damaged something. Has anyone else encountered this issue and what was the resolution? I have Torque Pro, but no tech 2. Is there something I can try diagnose this issue?

I'll look the codes up when I get a minute and see if they have anything in common.

how old is the battery? if it's still flooded lead acid, they don't like being run down to dead. might be worth replacing it before you go really deep into trouble shooting.


I had the battery that came with the truck go dead, I bought it used. replaced it with a acdelco agm battery from rock auto. all has been good for a few years now. load tested it a few weeks ago and it still tested at full capacity. so I think agm is a good battery for these trucks. I ran it dead once, didn't realize just the first click of the key without any dash lights on so I could have it in netrual still pulls over 10amps. ran this battery down to far to start. being agm, it came back. but I also always remove a battery terminal to charge them. Amazingly picky these trucks are, sadly we only really learn about them after they breakdown.

p0700 says that the (TCM) Transmission control module, sent a request for the ecm to turn on the check engine light. without a tcm code, you won't know why. if I had to guess, low voltage on the 12v circuit.

p2534 is fuel pump control module.

ignition 1 switch circuit low voltage. fpcm detects ign voltage less than 6 volts.


that's all on the 12v side of things, my guess is the battery doesn't have enough capacity left to hold the voltage up which it's going thru it's pre start checks. it doesn't need start motor cranking level, but still needs a good amount of power. could also be weak connection at the battery terminals.


might be a good idea to invest in a clone tech 2. it will read that tranny code for you that tq app won't show and show you the freeze frame data of what was happening when codes set. it's pretty priceless to have on hand with this trucks. if I go on trips, I take mine with me. if you break down traveling, no will be able to fix these. you'll have to know what you need done and quickly to get on the road. at 300$ it's money well spent.

Halomez said:

I accidentally ran my 12V battery dead three weeks ago. After recharging it with my trusty Craftsman battery charger it randomly decides to either not start or it will start and shut off with the message "SERVICE POWER STEERING". When it doesn't start I get two DTC codes:
P0700 - trans ctrl sys error
P2534 - ignition switch run/start position circuit low

These don't seem related. It was very intermittent at first, but now it's getting more frequent. I'm afraid the charge/jump damaged something. Has anyone else encountered this issue and what was the resolution? I have Torque Pro, but no tech 2. Is there something I can try diagnose this issue?

Click to expand...

there's another thing it could be. you'd need a scanner to pull p1 codes but I stumbled across this tidbit of programming from gm.

P1A4E
Individual hybrid battery voltage measurement is greater than 20.4 volts for 4 seconds.

Action Taken When the DTC Sets
• The BECM will request the HPCM to open the HV contactor relays


as any rechargeable battery gets weak, it's voltage will sag lower with the same load put in it. but the flip side no one really talks about is when it's charging the battery voltage will rise faster. Basically the less Capacity the bigger the voltage swings.

these packs don't cool nearly well enough, so you get one end OK ish the other end shot. a simple rear ac duct to the battery air intake might have saved these trucks from an early grave. but anyways, when you are regen charging, usually as you're coming to a stop, the cell voltages come up, if it sees one over 20.4v for 4 seconds it opens the main contactor. which that would be a good idea to keep from damaging a battery further, but it also kills the entire truck unexpectedly. it also doesn't have time to request a check engine light. because the bcm can't turn on the light itself, it's gotta set the code and then sent a request to the ecm over the can bus. the whole truck is dead long before that, even before you realize it, since the engine is already off and you don't lose brakes for a bit like a normal truck because of the 2000psi accumulator.

but the unexpected main power cut is enough for a low voltage code to be saved by the power steering module, since it runs off 12v battery but controls the 42v supply to the rack motor. enough to see the flash of service power steering system fault pop up.



this is just what I see from reading the explanation of the system and watching what my own truck does. if you have a scanner that can read the bcm freeze frame data, look for a max voltage over 20.4 and you probably found your stalling and power steering fault. especially if it restarts pretty quickly. no code needs to be cleared. Just a key cycle and all cell voltage back to normal, which they will be since it's not being charged by regen.

Conditions for Clearing the DTC P1A4E


P1A4E
• The calculated battery voltage measurement is less than 390 volts.
• Each individual hybrid battery voltage measurement is less than 19.5 volts.


these trucks.