I bought a 2007 GMC Sierra Classic (95,000m) with stock Duramax LBZ motor to pull my 12,000lb trailer. All was well for a couple of months until I set out for a long trip around the Western States.
First indication of a problem was after 500 miles I got a Check Engine Light. I had this looked at by a GMC mechanic who said several fault codes were current including Vane Position Sensor problem, Turbo High Boost Pressure and Turbo Low Boost pressure. However, a couple of hours on the computer didn’t show any indication of a current problem, the codes were cleared and I carried on with my trip. A couple of days later CEL came on again. I decided to wait until I got to another GMC dealer in Arizona, who confirmed the same codes as before. By this time I was also experiencing occasional loss of power and increasing black exhaust smoke. He changed the vane position sensor and all seemed well until a couple of days later when the truck started again to lose power and create a lot of black smoke under acceleration. Motor starts and idles fine, but lacks that “diesel knock”…sounds like a gas motor revving between 1000 and 2000 rpm. But this time there was no CEL.
Despite another day at the dealership no problem could be found. Air filter and fuel filter changed, air induction system and intercooler checked for leaks, EGR valve removed and cleaned, mass airflow sensor removed and cleaned. Still black smoke and loss of power under acceleration.
Another three hours at a diesel specialist shop turned up nothing. Fuel additive was added to the tank and things seemed better for a while. However, next day loss of power and smoke again with a CEL that this time showed “excessive EGR flow” and “Park/Neutral switch Circuit Input High”.
For the last ten days or so the low power/smoke problem comes and goes with no particular pattern but seems to be getting worse, and the “excessive EGR flow” CEL appears once every few days and the “Park/Neutral switch Circuit Input High” CEL every trip.
I’m looking to this forum for anyone with similar experience with this type of problem and hopefully a resolution.
Anyone know of a good technician/shop in Montana with Duramax experience that may be able to help?
First indication of a problem was after 500 miles I got a Check Engine Light. I had this looked at by a GMC mechanic who said several fault codes were current including Vane Position Sensor problem, Turbo High Boost Pressure and Turbo Low Boost pressure. However, a couple of hours on the computer didn’t show any indication of a current problem, the codes were cleared and I carried on with my trip. A couple of days later CEL came on again. I decided to wait until I got to another GMC dealer in Arizona, who confirmed the same codes as before. By this time I was also experiencing occasional loss of power and increasing black exhaust smoke. He changed the vane position sensor and all seemed well until a couple of days later when the truck started again to lose power and create a lot of black smoke under acceleration. Motor starts and idles fine, but lacks that “diesel knock”…sounds like a gas motor revving between 1000 and 2000 rpm. But this time there was no CEL.
Despite another day at the dealership no problem could be found. Air filter and fuel filter changed, air induction system and intercooler checked for leaks, EGR valve removed and cleaned, mass airflow sensor removed and cleaned. Still black smoke and loss of power under acceleration.
Another three hours at a diesel specialist shop turned up nothing. Fuel additive was added to the tank and things seemed better for a while. However, next day loss of power and smoke again with a CEL that this time showed “excessive EGR flow” and “Park/Neutral switch Circuit Input High”.
For the last ten days or so the low power/smoke problem comes and goes with no particular pattern but seems to be getting worse, and the “excessive EGR flow” CEL appears once every few days and the “Park/Neutral switch Circuit Input High” CEL every trip.
I’m looking to this forum for anyone with similar experience with this type of problem and hopefully a resolution.
Anyone know of a good technician/shop in Montana with Duramax experience that may be able to help?
