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?
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.
