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ggoodes

Dreaded "Reduced Engine Performance" Gremlins

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Apologies for the very long unload of details here, but possibly my V70R journey will help another poor soul out there avoid selling their ride in frustration!

I have a 2004 V70R that has given me many years of great driving pleasure, but about a year ago coughed up the "Reduced Engine Performance" message at the end of a 4-hour highway session in heavy rain and went into limp-mode: Heart-in-mouth, I pulled over safely, and turned the car off-and-on, which cleared the message and restored normal operation.  Since then, the car has been an increasingly cantankerous electronic fault-code generating machine, with everything from "No Oil Pressure, Stop Safely" to innumerable OBDII codes such as "Random Misfire", EVAP, throttle position-sensor, etc.  My mechanic ended up replacing the ETM since many of the codes implicated that, and the limp-mode symptoms did disappear for a while, but then began to arise again.

As the car had previously had a driver's foot-well flood which took out the SUM module (why the hell is there a CAN-bus module under the carpeting in the foot-well?) and caused a lot of scary codes and messages, I assumed these issues might be due to some corrosion or other problems with the wiring harness, especially as my (quite good) mechanic could never isolate a fault.  Then I got the "Alarm System Service Required" message, which basically came on every morning, and then cleared for the rest of the day (internet wisdom suggested this was a dying/dead NiCad battery in the driver's wheel-well).  The "Alarm System.." message I could live with, but I also got weekly check-engines which were a random selection of Misfire, EVAP, and throttle-sensor errors, to the point where my mechanic was considering another ETM replacement, which I could not believe should be needed (though would likely have been under warranty).  There were many strange voodoo-like aspects to the limp-mode symptom, including that it would be triggered by hitting a pot-hole, heavy-rain, and even a high degree of correlation with one particularly sharp right-turn I had to take on my daily commute (literally three days in a row in exactly that spot!)

Then I started getting "Chassis Settings Service Required" which is what I got when the SUM module was flooded, and at that point I was starting to consider ditching this car.  The AC clutch was failing, and we've had about a month of 90 degree weather in Ottawa, so this seemed like "Time To Die" as Roy Batty said in Bladerunner, but I needed the car for a few more trips and decided to give it one last session with the mechanic and at least get the AC working again.  Despite my opinion that the "Chassis Settings.." message was the least likely to be repairable, I asked my guy to look into it (my code-reader doesn't recognize the SUM module), and there were apparently a dozen or so sensor-codes.  However, he found that I needed new sway-bar end-links, and in the process of fixing that noticed that one of the sensors on the passenger-side wheel was wrapped around the drive axle and that the wiring had been shredded.  He moved and repaired the wiring, and this fixed the "Chassis Settings.." message.  All good!

But I also noticed that for the first time in 4 months, the "Alarm System.." messages were gone.  And, it's been over a week with no Check Engine!  A bit too soon to tell if the limp-mode is gone, but I'm beginning to have a theory: It's possible that the shredded wiring in the passenger-side wheel was exposing the sensor-bus of the car to random electrical noise.  Water, salt, bumps, even sharp turns would generate electrical signals which the computers could interpret as random crap.  I'm beginning to think (hope!) that the car is actually just fine and that a single set of wires was the source of the problem!

I will give an update after a few more weeks of driving, but I wanted to publicize this information to the group in case others are struggling with similarly vexing electronic gremlins:  All these sensors are electrically on the same bus (witness how the "Alarm System.." message can end up with non-functional sunroof situations), and so it's worth looking for a seemingly unrelated sensor problem when the OBDII codes are telling you something that doesn't make sense!

grant..

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