2000 V70R - Intermittent Major Electrical Fault

tightmopedman9 · Post by **tightmopedman9** » 15 Jan 2015, 19:55

Occasionally while driving the speedometer, tach and mileage indicator will stop functioning. This is associated with a flashing trans light, CEL, brake light and ABS light. When it happens the car goes into limp mode and stays in 3rd gear. Sometimes when it happens it feels as if idling on only 4 cylinders, but becomes smooth as soon as I start accelerating.

I've been in a conversation with the techs who have serviced this car for the past 8 years and they say that they've had this car in for this same problem multiple times in the past 2-3 years. They've tried multiple ABS computers, even one new ABS computer from Volvo (the current ABS computer in the car). They had an S70 which had the same problem and coincidentally happened to be in the shop the same time the V70R was in. For the S70 they sent every module into Xemodex for testing and everything came back fine. They noticed that when the problem occurred the ECM would drop off the CAN-BUS network, even though the car was still running. They cleaned the ECM contacts at the same time as replacing the ECM relay and the problem was fixed.

I've replaced the ECM relay on the V70R and cleaned the contacts on the ECM, but the problem persists. Admittedly, the relay was from a junkyard car, but after taking apart the relay and seeing how simple it is I doubt it could be the culprit. Also, the resistance was the same for both relays (95Ω) which also matched the resistance on a known working relay and is close to the value specified in VIDA (85Ω).

I read in another thread that someone had a similar problem which was resolved by fixing a loose engine ground.

Post by **abscate** » 16 Jan 2015, 06:54

Grounds can definitely mess up these cars and are easy to fix. Get the wiring diagram and find every one, clean to shiny metal, re torque bolts.

Tough problem, keep the faith!

Post by **cn90** » 16 Jan 2015, 07:16

Either ground cables (or engine ground straps) issue or...

Electrical portion of the ignition switch.

tightmopedman9 · Post by **tightmopedman9** » 16 Jan 2015, 09:59

The ignition switch did give me the 'round and round' spin the other day. I'll try jiggling the key when I get the problem again.

Post by **scot850** » 16 Jan 2015, 10:14

This is a tough break! I had problems with my 2000 V70R ignition switch which caused problems and flashed all sorts of issues.

Replaced the switch and all was then good.

Other issues that may cause the problems, especially the spinning key issue:

- Bad key or proximity chip in it? I had a new Volvo key and it just spun in the lock even after programming. Turned out to be a badly cut key by Volvo.

- Perhaps an issue with the security system?

- Also, although I'm sure you have done this, while checking the earth connections, also check the condition of the B+ cable in the main fuse box (the triangular one near the LH strut in the engine bay. Open it up and look down at the front corner of it and check to see if the cable end with the nut on it is bright and shiny. If it is not, change it. Mine was melted and burnt on removal. They can short out and go on fire in worst case.

Good luck!

Neil.

tightmopedman9 · Post by **tightmopedman9** » 16 Jan 2015, 12:30

I checked all the grounds with the car off and the car running and got no voltage drop to any ground location. The B+ cable to the main fuse box is in great condition, still minty fresh.

Scot, what symptoms were your experiencing that were relieved with replacement of the ignition switch?

Post by **misha** » 16 Jan 2015, 12:43

tightmopedman9 wrote:...what symptoms were your experiencing that were relieved with replacement of the ignition switch?

Those symptoms you have are symptoms of a bad/failing ignition switch.Like somebody allready suggested...try wigling the key while it's in ignition when those problems appear.

Post by **scot850** » 16 Jan 2015, 23:05

Sometimes the key would spin, the dash notification lights wouldn't always light up or some would be darker than the rest. Car would run rough on start up, switch off, re-start and all would be good.

Neil.

tightmopedman9 · Post by **tightmopedman9** » 17 Jan 2015, 14:46

So, driving the car in stop and go traffic the problem occurred after about 5 miles of driving. No amount of jiggling the key, hitting the steering column or restarting the car would fix the problem.

I got to my garage and cut a piece of 1/8" thick wood and placed it in between the ABS computer main plug and ABS pump. The problem has not reoccurred in over 25 miles of driving; usually the problem occurs within a few minutes of driving the car.

I will report back if the problem reoccurs.

Post by **Ozark Lee** » 17 Jan 2015, 16:52

tightmopedman9 wrote:I got to my garage and cut a piece of 1/8" thick wood and placed it in between the ABS computer main plug and ABS pump.

That may or may not be telling you anything but it stresses the contact pins on the ABS module and it can lead to problems where there really were none before. The wood wedge trick is typically used to try to cure a bad module but it never works over the long run.

The terrible thing about intermittent problems is - well - that they are intermittent. They will drive you out of your mind and routine testing for bad components often never reveals the true source of the problem. I had similar problems with my '99 XC where sometimes it would start and sometimes it wouldn't. I think I finally cured it by getting the ECU data cloned into a different module at ARD Tuning. I tried every diagnostic trick I could think of and at one point I had two dual trace oscilloscopes and two DVMs monitoring things so that I could try to see what was going on while I cranked the car. Even with all of the diagnostics I couldn't come up with a part that was just bad.

...Lee