Author Topic: Inaccurate High Boost Pressure  (Read 152 times)

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Offline Papa Dave

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Inaccurate High Boost Pressure
« on: November 03, 2020, 10:38:31 PM »
I have a 2005 Winnebago Journey with the Freightliner chassis and Cat C7 engine.  I have had performance issues with occasional STOP ENGINE/ CHECK ENGINE alarms (fault code 102-07).  To better monitor engine operating parameters and diagnostics I have a ScanGauge D display module attached to the J1939 data port.  I also have added a secondary boost sensor with a pneumatic boost gauge on my dash.  By comparing the pneumatic boost gauge reading to the boost pressure displayed off the data port on the ScanGauge module when the occasional STOP ENGINE/ CHECK ENGINE condition occurs, it appears that the boost pressure reported off the data port is inaccurately high (28-29 PSI while the pneumatic gauge shows 25-26 PSI.)  These alarm events typically occur while climbing hills with maximum throttle and the alarm condition clears when the throttle is reduced.  Most of the time the two boost readings match.  Assuming the pneumatic gauge is accurate, what would cause the primary boost sensor to report an inaccurately high reading on the data port? 

Offline LPD218

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Re: Inaccurate High Boost Pressure
« Reply #1 on: November 04, 2020, 09:56:31 AM »
Papa,
I had the same code and exact issue as you in my 2004 C7.  With the help of the forums, I traced it to a stuck waste gate on the turbo.  I had to replace the turbo charger as the gate was nice and frozen.

Offline David.e.atherton

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Re: Inaccurate High Boost Pressure
« Reply #2 on: November 04, 2020, 12:32:47 PM »
Papa Dave, the fault code of 102-7  indicates boost pressure sensor fault . My suggestion
before you replace the turbocharger because of possible stuck wastegate on the turbo, I
Would change the boost pressure sensor. Ask Dave, Dave Atherton Retired Cat Mechanic.


Offline Papa Dave

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Re: Inaccurate High Boost Pressure
« Reply #3 on: November 05, 2020, 08:56:02 PM »
Thanks guys for your input.  The boost sensor was replaced less than a year ago.  But I suppose it could be defective from the manufacturer.  Given the cost to replace the turbo, it makes sense to try a new boost sensor first.