Your diagnostic shows a C1246 code. Should the tech not have performed this diagnostic?? To determine or verify communication from PCM/ECU to skid control/abs module...
C1223 is an ABS Control System Malfunction and the C1246 is the Master Cylinder Pressure Sensor Malfunction.
I would manually pull ALL the codes also to get a better idea of what's going on. There may be more DTC codes related to your skid/abs modules inputs/sensors than just the brake lamp switch with can cause it to disable your abs related functions.. Like I mentioned earlier he only followed the flow chart for the stop lamp switch..
C1223 is literally "Hey, I have an issue in the ABS/VSC/TRAC system" much in the same way the ABS module sets a C1201- Engine Control Malfunction when the check engine light sets, regardless of what actual problem the ECM has. It's a DTC that directs you to the trouble module, the FSM literally just has you go"Is there a C1223? Check ABS System for other ABS/VSC/TRAC DTCs and diagnose those first." It's slightly more useful that the P1604-Startability Malfunction that every damn Toyota sets and literally means nothing and almost every car has it stored.
So you'd basically just disregard the C1223 in this case because we already know the issue is in the ABS/VSC/TRAC system, so you'd just look at the C1246-Master Cylinder Pressure Sensor Malfunction issue. If you look at the troubleshooting tree for that DTC you'll see that listed as possible problem areas are: Master cylinder pressure sensor, Master cylinder pressure sensor circuit,
Stop light switch circuit, Master cylinder solenoid.
Something to note is that the reason the Stop Light Switch Circuit is a possible trouble area is because the Skid Control ECU is using the brake switch signal fed to it via the STP pin to verify that pressure changes match what it should see against it's internal table when the pedal is pressed; if the circuit is faulty the Skid Control ECU doesn't know that the pedal is being pressed and thus cannot be sure that the pressures and/or sensor are accurate to what it should see.
That coupled with the customer's original concern regarding the brake lights always being on would mean the best place to start and rule things out is the brake light circuit which is what the technician appears to have done. In the course of that diagnostics they determined that the Skid Control ECU is faulty per their checks.
i do do my own work whenever i can. this electric issue has been beyond me so far, though maybe not the actual fix). i am going to put together a documented complaint to send to the service manager. contemplating contacting cc company to file a dispute/damage claim.
I would bring that up to the service writer and the service manager. It's very likely the technician who did your oil change & multi-point and the technician who did the diagnosis are not the same person. It's common when the shop's busy to have Lube Bay do the "easy stuff" like oil changes, tire change outs, etc. and then have more critical or better paying work sent to the back shop for certified technicians to do. Technically speaking if a Lube Tech sees something like that and they're not sure what to write down (because it seems like most of them barely know which end their pants go on...) they're supposed to notify a service writer and/or grab a technician to double-check and make sure it gets noted down.
So I would politely (or not, it's up to you) mention to the service writer and the service manager that this was missed on your inspection and you are unhappy. Maybe they'll give you a refund on the oil change, or a free detail, or something I don't know how they do business over there... I would hope they would go chew out the Lube Tech who missed that and make sure that it doesn't happen again, but let's be real here.
I get your waning confidence in the work done to your vehicle. I personally get annoyed when lube bay does something like miss an item on a customer's car or not clean up a mess and the customer thinks I was the one who did that, it happens more often than I'd like. As for the technician's initial diagnosis regarding the Skid Control ECU being faulty, I do see the logic there and his testing does seem to indicate that is the likely culprit; though as I mentioned above, there is one or two points that stick out to me and I'd want to rule them out personally before fully committing to that diagnosis. But again, I wasn't there when the vehicle was brought in, scanned, diagnosed, and I haven't seen the customer's concern myself either; so I am just arm chair wrenching here.
