Hey everyone,
Trying to narrow down a few issues on my S80 2.5T and could use some insight.
Symptoms
- Strong jolt/clunk when shifting into reverse.
- Jolt when accelerating hard from a complete stop (sometimes again if throttle is held right after).
- Smooth in the rest of the gears under normal driving.
- Reverse engages smoothly and will roll back without gas.
- ATF fluid is bright red but overfilled.
- PCV glove test: glove only pulls vacuum when revved, not at idle.
- Large oil leaks; a couple hoses look swollen/spongy.
- One engine-to-chassis ground strap is coated in oil.
- Harness junction by radiator fan may be contributing to multiple, sometimes unrelated, codes.
Codes Present
Powertrain
- P0101 — Mass or Volume Air Flow Circuit Range/Performance
- 002E — Lock-up Function: Transmission Jerks at Lock-Up
ABS Module
- 0041 — Wheel Sensor, Right Rear Faulty Signal
- 0031 — Wheel Sensor, Left Rear Faulty Signal
- 0057 — Power Supply Voltage Too Low
- 0061 — Brake Discs Temperature Too High
What’s been checked/done
- PCV smoke test showed no leaks with engine off.
- Ground points inspected/cleaned.
- Not yet drained ATF to spec (still overfilled).
Questions
- Are these jolts more likely a valve body/solenoid issue, bad grounds/electrical, or PCV/vacuum related?
- Could ATF overfill alone cause or mask these symptoms?
- Any suggested order of diagnosis before throwing parts at it?
Thanks in advance!
So first address all the trouble codes. Two places you can find remedies:
Strong jolt/clunk when shifting into reverse.
Check your engine and transmission mounts.
ATF fluid is bright red but overfilled.
obviously you need to adjust it to the correct level. Transmission can't function properly if vents are blocked and damage may even result.\
PCV glove test: glove only pulls vacuum when revved, not at idle.
PCV stands for POSITIVE crankcase ventilation. Vacuum is negative. If it's 20 years old just replace it. They usually don't cost much
Large oil leaks; a couple hoses look swollen/spongy.
obviously replace them.
One engine-to-chassis ground strap is coated in oil.
Good . Free corrosion protection. Just make sure all the copper is there.
Harness junction by radiator fan may be contributing to multiple, sometimes unrelated, codes.
fix it
@imperator Appreciate the tips. I’m going through each code in order I plan on checking grounds, charging system & power supply, abs system, rear axle and suspension, and resetting in that order before committing to a transmission specific check with a carsoft V2. Just wanted to be sure if really that was the best way to go than to just throw parts at it. Will be checking mounts though and replacing pcv once I can pinpoint what’s causing the jolts I’m experiencing. Sure enough this isn’t a rapid fire situation right?
@imperator I guess I feel like I’m looking at something a little more complicated on paper…
than to just throw parts at it.
I never advocate for the parts cannon approach. However I think a PCV valve would technically require a complex setup to test the exact ranges of pressure when it opens/closes etc. and for the $10 or whatever it usually costs, it's just not worth the time.
this isn’t a rapid fire situation right?
rapid fire... are you asking if it's urgent?
I would definitely adjust the fluid level asap. Spongy hoses don't really inspire confidence.Neither does a janky harness. Worn mounts are going to wear out other driveline components. Bad wheel sensors = bad braking. overheating brakes = bad braking. P0101 means poor economy and possibly catalyst wear.... you have your work cut out for you.
@imperator By “rapid fire” I meant throwing parts at it without confirming the cause first, not that I’m dragging my feet. I get what you’re saying though; some of these things (fluid level, harness, mounts, brakes) can cause other problems if left alone. I’m prioritizing fluid level and grounds first, then working my way down the list. Hoping that gets rid of the jolts before I dive into the deeper stuff.
it's an almost 20yo car. Be ready for the possibility that the transmission is totally worn out.
@imperator well good and bad news 😂 a bath rag accidentally got sucked into the intake hose after the MAF. It partially blocked airflow, but the car still ran. While it was in there, every jolt/clunk issue I’ve been chasing in reverse and from a stop completely disappeared. I work pretty quick if I do say so myself 🤭
lucky
@imperator oh i ain’t checked yet to see if it made it past the turbo but the clunk was gone i called it a night that’s definitely one way to do it though 😂