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Discussion Starter · #1 ·
1999 Volvo S70 2.4L NonT 122K (bought used at 38K 2003) Generally reliable for 4 yrs, expensive last year and a half. Seen the old ChkEng Light too much, too many trips to Dealer. Never sure whether I am getting honest info. Never sure the Dealer really knows what they are doing, or actually did work billed, since several problems reoccured. Bought OBD2 device to read codes (DTC's) on my PC.

Car runs fine but ChkEng Light comes on. OBD2 DTC's = (4)
P1081 (Immobilizer Communication?),
P0600 (Serial Communication Link Malfunction),
P0722 (Transmission Speed Sensor Missing or Output Speed Sensor Circuit -No Signal),
P1057 (?Not sure?- Possible TCM Fault- Possibly involving Throtle Module - opinions & sources vary)
I erase all codes and turn off ChkEng Light with OBD2 device & computer.
Vehicle drives fine for 2 weeks (60-80 miles, mostly local, some highway.

Hook up OBDCOM device to Vehicle just to see if any codes have returned.
Scanner Program reports CODE P1081 is stored, but ChkEng Light has not come on. No other codes are reported. Vehicle continues to drive fine.

YESTERDAY (10-12 miles later)
ChkEng Light come on again. I hook up OBD2 device and PC to car to read codes and monitor and record vehicle operation and sensor data while driving. OBD2 DTC's = (4) The same four DTC's as before.
P0600 (reported by sensor # 122)
P1057 (reported by sensor # 122)
P1081 (reported by Sensor # 122)
P0722 (reported by sensor # 31)

DTC's are reported in the order listed.
See definitions of DTC's above - (as far as I can determine definitions)

A minute or two later, the (lighted) upward pointing ARROW starts flashing continuously in the instrument pannel window where the ChkEng Light and other warning lights are located. Car still in PARK. (This lighted arrow usually only appears when the vehicle is in a gear below D, and then it stays on {not flasing} until the shifter is moved up to D. Engine still ran smooth, so I took the car for a short drive hooked up to the computer, and recored operational data.

A mile or two later, while on the higway, the ABS and BRAKE lights came on then turned off, and repeated this cylcle intermitently throughout the drive. The speedometer also stopped working (or dropped to zero while driving 60MPH) and the odometer reading turned into a line of dashes, then both came back on, and repeated a cycle of intermitent malfunction throughout the drive. Please NOTE, the vehicle continued to operate normally and the brakes worked fine.


I won't be fixing it myself, but I hate to take it to the dealer for another expensive round of repairs that may, or may not, all be necessary and may, or may not, actually fix the car.

I have an honest local mechanic with some, but not lots of diagnostic equipment. He will competently do what I ask him to do, but it is better to know what work needs to be done or parts replaced. Then he will do what I asked for a fair price.

Any constructive advice or suggested solutions would be appreciated, hopefully from guys (or women) who know what they are talking about.



63,543 Posts
Re: Volvo DTC's on 99 S70 (4MRun)

I had these on a car, we repaired the ABS module and most codes were gone and no more CEL's
You may need a vehicle speed sensor too (not an ABS wheel sensor) but the speed sensor off the tranny. Not expensive, $80 and about 1/2 hour labor
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