Interpretting OBDII data

So this is a follow up to my previous post about EGR and turbo issues.

I've got a 2007 Dodge Sprinter 170" WB. -- 55,000 miles

I've had intermittent issues going into limp mode. I plan on changing the 2 intercooler hoses along with the intake air sensor and cleaning the EGR but it's too cold here in chicago without a garage.

Codes I've retrieved in the past are P0234 (turbocharger/superbooster overboost condition), P0471 (exhaust pressure sensor a circuit range/performance), P0473 (exhaust pressure sensor a circuit high input).

I had a rusted tail pipe right after the muffler that had been disconnected, just had that fixed yesterday

I had this scanned with the MB scan tool and was told i needed a new turbo because the actuator or regulator was bad.

Mind you , these are intermittent issues.

Latest code i retrieved a few days ago was P0234. Here's the freeze data:
Abslt TPS% 80.8
Eng Speed 2143
Baro Press 28.3
Calc Load 48.2
MAF 111.26
MAP 58.2
Out Temp 41
Coolant 120
IAT 64
VEH Speed 31 mph
ABS FRP 9127.22
REL TPS 12.9
ACC POS D 29.0
ACC POS E 29.0
EGR ERR -23.4
EGR CMD 32.6
FUEL 53.7
VPWR 12.98

How do you know if something is wrong with the EGR valve (i.e. dirty) or if it's truly a bad turbo regulator? Should the EGR err% be 0 ? I'd appreciate any help. Thanks.


Well-known member
Diagnosing from a data list is very difficult task and basically an expert skill. For the novice and some expects will often compare data values to a "known good" vehicle. (Experts are very hard to find.). The freeze data is a just a small sample of the data At the moment the code stored. The true data stream is the real list to figure out what's going on.

That said I would say there is a 99.5% chance you do NOT need a new turbo.

There is a equal chance you have an EGR problem directly related to the EGR valve, the EGR cooler, the two EGR temp sensors and the EGR pressure sensor. Replacing the parts from this list is not the way to fix this.

While the air intake temp sensor has been an issue years back it might be the easiest sensor to check on a data list. Cold engine, key on the temp sensor would read the actual air temp on the data list. It is not likely your problem. The turbo hoses and checking the gasket on the front of the turbo they are almost maintenance items for a sprinter. Careful detailed inspection of all the hoses and connections, o-rings, clamps and sensors connections makes perfect sense. Then make a decision on which parts to replace.

The codes and data your seeing is coming from what scan tool ? This is important and there may be other permanent and temporary codes stored that will give more info on the exact area of the problem.
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Thanks for the showkey. That was my take on it as well.

I'm using an actron CP9575. I also ordered an ultragauge that I plan on installing on a semi-permanent basis. I know the real time data at that moment, and what symptoms/results that happen after the fault can explain more. I guess I'm looking for things I should look for when it occurs. The egr values stood out to me. Am I right that according to the data, the ecm is calling for 32.6% but the egr err shows -23.4%. So the egr valve only opening roughly 9% ? Seems like that's my starting point to checkout/clean.

There is oil residue near the charge air hose going into the intercooler so I figured it might be time to replace those hoses premtively. And I've read others post about IAT sensor causing same issue, for $22 I'm up for it too.

As an electrical contractor, I've never had the mindset of being a "parts changer", I want to find the problem and correct it.

I have this love/hate relationship with my truck right now.

I wish it wasn't such an intermittent issue, it would be much easier to pinpoint. Thanks for any additional info you can provide.

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