2004 XC90 2.5T Intermittent Overboost only w/Cruise Control

dtarullo · Post by **dtarullo** » 05 Apr 2014, 15:27

I have a 2004 Volvo XC90 2.5T with 121xxx miles. We were running on the interstate at 75mph with cruise on, when we ran thru a dip in the road surface, which was enough to jar the car upward, at the moment we hit, the cruise shut off and the power dropped to the 'reduced engine Performance' mode and could not hold any speed. Cleared the road and after shutting-off the motor and restarting, the car ran fine, until on the return trip under same circumstances - 75mph w/cruise on, hit a dip in the road and the message center again read 'reduced engine Performance' mode. I cleared the problem the same way and continued driving. Completed the trip without using the Cruise Control (several hours more driving) and did not encounter the problem again nor over the week since – have not used cruise control since that trip. I scanned the ODBII using my CarMD scan tool and got the secondary code P0234 (Turbo Charger Overboost Condition) with a description saying it is an intermittent problem. Fyi, recently had the full timing belt job completed. Do you have any recommendations on the cause of the problem? Any ideas on what the cause could be would be greatly appreciated. Thanks

huzzsaba · Post by **huzzsaba** » 06 Apr 2014, 08:41

Its possible its just impact of the dip and the cruise control trying to keep up after taking a hit. Sounds like a pretty serious dip to have a jarring effect.

Just clear the codes and see if it comes back under normal driving conditions.

dtarullo · Post by **dtarullo** » 07 Apr 2014, 20:31

We've made that trip many times over the past several years, hitting the same and all the dips in the road with no negative effects. I don't think the dip in the road (just prior and following an interstate bridge) was/is excessive, just noticeable and enough to obviously shake something to have an effect. I cleared the code and will test again the next time a take the highway. Thanks.

huzzsaba · Post by **huzzsaba** » 08 Apr 2014, 14:07

One other thing that comes to mind that you can replace is the TCV (Turbo Control Valve). I replaced mine due to weird oscillating behavior of the throttle while going uphill with the cruise control on. There was no check engine light on, but I figured given the mileage on the car, it should be replaced anyways.