2000 V 70 XC thermostat causing P0422

Post by **kahl** » 13 Aug 2014, 08:35

Hi guys, On my new to me 2000 V70 XC I have been through many codes and am trying to solve the P0422 code that comes up sometimes. I have focused on the thermostat. On the other Volvos the temperature indicater will be in the 3 O'clock position within 3 or 4 miles of driving. This car the thermostat takes a good 12 to 15 miles of driving before it will slide into the 3O'clock position. My thinking is that due to a faulty thermostat the engine is running rich. This rich running will then trigger the P 0422 code. I noticed that when I let off the gas after running 55MPH for about 10 miles the code will trigger.

I smoked the intake side with no vacuum leaks. Compression is consistent in all cylinders. Exhaust has no leakers. Throttle body is good.

Any thoughts?
thanks,
Stew

Post by **erikv11** » 13 Aug 2014, 08:42

That's a good theory, I'm sold on it. And the stat is definitely opening too slowly, so swap it out and see if you were right!

Post by **xHeart** » 13 Aug 2014, 08:53

erikv11 wrote:That's a good theory, I'm sold on it. And the stat is definitely opening too slowly, so swap it out and see if you were right!

+1
Very likely solved for $10.

Post by **kahl** » 03 Feb 2015, 20:49

The thermostat had no affect on my P0422. I hope now I have found the smoking gun. I found an exhaust leak on the exhaust manifold at cylinder 1. Changed out the exhaust manifold gaskets. Being beat up by this dragon I am yet to claim victory. Here is a picture of the broken up gasket.

Post by **erikv11** » 03 Feb 2015, 22:45

Just out of curiosity, with the new stat does the car warm up more quickly?

Post by **kahl** » 03 Feb 2015, 22:56

With the new thermostat the car warms up more quickly and is stable at the 3 o'clock position. This car did have a defective thermostat. Replacing thermostat had no impact on P0422.

Post by **erikv11** » 03 Feb 2015, 23:32

When it rains, it pours ...

Sounds like you found it though with the exhaust leak, hope it holds up.

Post by **precopster** » 04 Feb 2015, 04:11

I wonder if it's a combination of bad t stat and out of tolerance ECT. Has the ECT been changed?

Last week I helped an ETM customer solve a no start situation by suggesting he replace the t stat and ECT on a 1999 V70XC. He measured the ECT in a pot of water with a cooking thermometer and found it was open circuit. The t stat had a broken wing as per the photo he messaged to me:

He placed a 1.5K resistor in place of the ECT and it fired right up

Post by **kahl** » 21 Apr 2015, 16:13

I finally got this code to go away without pulling the CEl lamp. Changed out the rear O2 sensor two weeks ago. I put the car through a several drive cycles and no CEL illumination. This car is now squak free!!!!