Accelerator issue, random downshift (auto), ESP off

[Skylarking]

Sorry Nb, must have missed that failed cats were primer for a full on zorst

As to the O2 sensor, 0.0V is either a completely dead sensor (not the case since you swapped sensors and fault didnt move with the sensor) or plug is not pushed in or doesn't make correct contact with the pins or you have a harness issue (open circuit in O2 sensor wire to ECU).

As to engine/trans controller, I always assumed all controllers went through power on self test and if there were issues, a DTC is set. But I don’t think you’ve said a TCM or ECU specific DTC was ever found. Hopefully the new throttle body will sort out the issue (since faulty input = faulty output).

 

[bulkbogan]

Hey mate,

Check my post history. I had the EXACT same constellation of symptoms and couldn't find anyone else who had experienced it.

It was my brake pedal switch (little plastic doohicky behind the pedal). After all the dramas trying to diagnose it, I took it to a mate at Holden who plugged in a tech2 and identified the switch had been replaced at one point, and not re-learned. He had to go through some procedure to get the ECU to understand the positioning of the sensor relative to the voltage it was supplying the ECU. Problem completely gone, after a year or two of pulling my hair out.

If you think about it, it makes sense. ESP is coming on because your car thinks it is braking. It's downshifting to match what it thinks is braking. I bet your cruise control cuts off randomly too?

Anyway, check that out.

 

[bulkbogan]

Hey all
I bought a ve sv6 2008.5 with 120,000, now 150,000. It has had these issues the entire time. I have spent many hours searching forums and asking around, I cant find any help for this issue.
I'll explain the issues then what I have done to try and fix.

The ESP comes on at random when driving +10 mins. (Also no cruise control)

When cruising maintaining 80-120km/hr it will randomly downshift from 5th to 4th for 3 seconds then downshift to 3rd (even at 110km/hr) at 4krpm and hold for 5 seconds then back to 5th for 10 seconds then repeat for up to a couple minutes. The only theme I've found is hills increase the chance of this happening, but it happens on flat highway.

When maintaining a speed and not shifting the accelerator pedal it sometimes (once every 20 mins or so) wont register any increased throttle even flat foot it will maintain the current speed forever until I release throttle completely and it fixes immediately.

None of these create an engine code.


I have replaced bank 1 o2 sensors, accelerator pedal, transmission serviced, all new tires, (there were failing cats so i) fitted full system exhaust, extractors, hi flow cats.
Since fitting the extractors it registers an engine code for o2 sensor 1 bank 2 but should not be related since the problems occured before this and havnt changed.

Any ideas would be greatly appreciated as im stumped and spending a lot o money without fixing the issues. Thanks!

See my last reply dude? Genuinely curious to see if I was right.

 

[Nb VEsv6]

As to the O2 sensor, 0.0V is either a completely dead sensor (not the case since you swapped sensors and fault didnt move with the sensor) or plug is not pushed in or doesn't make correct contact with the pins or you have a harness issue (open circuit in O2 sensor wire to ECU).

Hey sorry I've been caught up at work.. I took it to an auto electrician shop and they found that the pins in the harness plug were a bit crooked and fixed them and cleared code. Driving home from the shop p0155 came up... I checked with my scan tool and both sides have proper voltage now, so that was fixed but theres a new code .. I'll take it back to them.

Hey bulkbogan thanks for the tip, I looked into that and I have no clue if the brake sensor has been replaced at all but the online symptoms are the closest to mine so far !
Aside from the gear changes, did you also have this strange accelerating issue?
The new TB has arrived so i'll fit that and take it for a drive to see if that works, if it doesn't then my next step would be checking out the brake sensor.
I'll be back from work on the weekend so I'll be able to update on that then.

 

[bulkbogan]

Hey sorry I've been caught up at work.. I took it to an auto electrician shop and they found that the pins in the harness plug were a bit crooked and fixed them and cleared code. Driving home from the shop p0155 came up... I checked with my scan tool and both sides have proper voltage now, so that was fixed but theres a new code .. I'll take it back to them.

Hey bulkbogan thanks for the tip, I looked into that and I have no clue if the brake sensor has been replaced at all but the online symptoms are the closest to mine so far !
Aside from the gear changes, did you also have this strange accelerating issue?
The new TB has arrived so i'll fit that and take it for a drive to see if that works, if it doesn't then my next step would be checking out the brake sensor.
I'll be back from work on the weekend so I'll be able to update on that then.

Yeah definitely, everything you've said is what mine would do. The random downshifts, getting stuck in gear, dead pedal. Seemed to happen out of nowhere but particularly on declines/inclines. These are all the exact same issues I had.

The dead pedal wasn't nearly as often as the downshifting issue though, but did happen occassionally. You almost develop a sense for when the car is going to spaz out because the pedal starts acting up.

I also replaced my entire engine loom (rats ate through it), throttle body, transmission, accelerator pedal trying to address this issue among others. You can imagine my reaction when I found out a $5 part needed to be learned. Pays to get proper diagnosis from a reputable mechanic, don't go throwing parts at the car without knowing what could be causing it. Learn from my mistakes and if it does end up being the pedal sensor - I'll feel a bit better saving someone from falling into the same trap.

 

[Nb VEsv6]

Yeah definitely, everything you've said is what mine would do. The random downshifts, getting stuck in gear, dead pedal. Seemed to happen out of nowhere but particularly on declines/inclines. These are all the exact same issues I had.

The dead pedal wasn't nearly as often as the downshifting issue though, but did happen occassionally. You almost develop a sense for when the car is going to spaz out because the pedal starts acting up.

I also replaced my entire engine loom (rats ate through it), throttle body, transmission, accelerator pedal trying to address this issue among others. You can imagine my reaction when I found out a $5 part needed to be learned. Pays to get proper diagnosis from a reputable mechanic, don't go throwing parts at the car without knowing what could be causing it. Learn from my mistakes and if it does end up being the pedal sensor - I'll feel a bit better saving someone from falling into the same trap.

So.. I could kiss the ground you walk lol
It's such relief hearing somebody describe exactly my cars issue, i could always tell when the pedal started playing up how tiny the difference i thought "here we go"
I didn't know you replied again until now sorry man but this is my update
New throttle body did no difference.
Havnt had time to take it to an auto elec to fix the o2 sensor code.

I found out my brake lights were stuck on most of the time, i spent a few hours laying under the steering wheel trying to adjust anything brake switch related.
I undid the screw holding the switch to the bracket mount and found a tiny (less than 1mm) play and tightened it back up in a position that moves the switch fork to a more rested position. Brake lights turn off when i take my foot off the brake now.

I just drove for 2 hours, an hour with cruise control no problems, an hour normal driving no problems.

I cannot thank you enough, i know the feeling, if this is the fix it cost me $0...