1999 S70 Serial Communications Link P0600

asummers · Post by **asummers** » 15 Oct 2014, 05:03

My S70 has been exhibiting symptoms of abs module failure, brake light, abs light, cel light, and up arrow flashing. But it has been off and on, and sometimes not all the lights. But one thing seems to be common, the mileage and trip reading will go blank with only a line of hyphens on both lines. That is when the brake and abs lights come on, and the tranny stays in 3rd gear limp mode. I have gotten the P0600 code Serial Communication Link Malfunction. Does anyone know where this communication link is actually located? Maybe it is the cause of it all?

Post by **Matty Moo** » 15 Oct 2014, 08:38

It isn't any actual link per se, it's just a communication code saying that communication has been cut. Usually in this case the module is no longer communicating to the ecu what it needs to know, which is the speed.

asummers · Post by **asummers** » 16 Oct 2014, 10:57

At least now it just has the flashing up arrow and cel lights on, no brake and abs lights right now. And, it isn't in limp mode either. Frustrating.

asummers · Post by **asummers** » 17 Oct 2014, 10:50

One more detail. For the last week we had rain almost every day, and I had problems with the abs, etc. Now we have had dry weather and there doesn't seem to be any problems right now. Hmmmm, a wet weather problem, what could cause that?

Post by **FLXC90** » 17 Oct 2014, 16:05

Wet weather

A crack in housing, or connector, imperfect ground, corrosion or gap in connector pins. Do a physical inspection, disconnect, clean and apply dielectric grease to connectors maybe? check which grounds apply to the system. In some of the other threads, and maybe Matty Moo's page I've read that some people open and close the connector cap a few times to re-establish contact at the big connector.

Post by **jimmy57** » 18 Oct 2014, 09:14

the network comm wires on that car are green and white and twisted. They run TCM to ECM to ETM on the RH side of engine compartment and a leg runs to ABS CM on LH side. The wires run to the instrument cluster as it is the network controller on that car.

asummers · Post by **asummers** » 22 Oct 2014, 12:44

When you said the instrument cluster is the network controller, that reminded me that the lights in the cluster have been going off too. The lights in the speedometer have been off and on, that may be happening when the comm link fails and the odometer and trip go to --------- and the speedometer doesn't work. I will have to watch for that the next time it fails at dark. The other lights stay on, and the tach and gauges still work during failure.

Post by **jimmy57** » 22 Oct 2014, 13:20

Tach is ECM sourced, speedo is ABS sourced, Trans relies on vehicle speed from ABS.

Have you ever lost throttle?

Full code read on the car would likely give codes that would be the clues.

alausch · Post by **alausch** » 02 Nov 2015, 12:32

I'm having the same issues with my 99 V70 2.4 (P0600, speedo stops working for a sec). But, I also have the P0722 Output Shaft Sensor code. If all of this is going on with a P0722 code, would it be more likely the sensor or ABS module?

VolvosLocos · Post by **VolvosLocos** » 27 Feb 2016, 15:22

I believe this is happening on My 1999 V70 due to a leaking radiator spraying water back onto the motor getting electrical components & connections wet.

Right?