Reduced Engine Power

[V70tdi]

I just had this 2008 for some weeks and got the Reduced Engine Power message poping up as soon i get on the accelerator. It can go on idle without any message.
Just have a sinple chinese Blotooth OBD reader and get C0300 and C0700 no other codes so i has to get me a better code reader.
Just could read EGR position and it calls for 0% and get 38% wrong position. Can a stuck EGR valve get the Reduced Engine Power ?
Any suggestions for a simple but good OBD tool that works on the Duramax ?

 

[2004LB7]

Some people have good luck with the torque app and the Bluetooth OBD module. Definitely cheap

I prefer a bidirectional scanner so you can command regeneration and other helpful items for diagnostics

There's a handful of threads on here regarding the Chinese GM Tech 2 that you might want to search and see if that will fit your needs

Off the top of my head, I don't believe EGR issues will cause a limp mode. Bit can cause a rough running engine or pour fuel mileage

The biggest reason for limp mode on these engines is low fuel pressure. Either a link in the fuel line causing it to suck air, a restriction like a kinked fuel line, plugged filter or in less common CP3 issues

Plugged DPF or a failed differential pressure sensor can do it too.

But to really know, you need a proper scanner that can give you the codes. Since you are likely too far away for any one here to read them for you

 

[gmduramax]

Is the truck stock?

 

[Ron Nielson]

I can't find those DTCs anywhere. Maybe wrong prefix?

 

[2004LB7]

C0300 rear speed sensor

C0700 could actually be the P0700 for transmission mil request. A possible reason for limp

 

[NC-smokinlmm]

What happens when you clear them?

 

[V70tdi]

Is the truck stock?

No it has a DPF delete and probably some tuning told by previous ouner. What kind of tuning is unknown for me. Also a aftermarket Volant cold air intake but I will try to find a original when its easyer to find airfilter to an original than the aftermarket one here in Sweden.

 

[V70tdi]

What happens when you clear them?

I remembered that i had an ELM 327 USB interface so i tested to read codes with that one but didnt get anything. But a delete with that one got the engine to run like before. Sadenly i got the Reduced engine power again after 2 short trips.
Looked at the MAF sensor and it was the dirtiest i ever seen. A fast clean with electronic cleener and a new code delete got the message to disapere for a longer time but now its back again. Will see if i can read more parameters with the ELM 327 later on. No CEL comes on at any time it happens so feels odd to me.

 

[2004LB7]

Could be tuning related. Always hard to diagnose when you have no idea what was done in the tune. But MAF sensor issues can cause the engine to run bad. They don't normally cause a reduced engine power but can cause a code. It's also possible the intake is a different size then the one on the tune and they don't play well with each other

Hard to say when you have a tune. But a better scanner will likely be needed to get all the appropriate codes to help us figure it out

 

[Chevy1925]

Is the egr and throttle blade plugged in or unplugged?

 

[V70tdi]

Is the egr and throttle blade plugged in or unplugged?

Plugged in.

 

[Chevy1925]

Unplug them and see what happens

 

[V70tdi]

Unplug them and see what happens

EGR unplugged nothing happens.
Trottle blade unplugged i get a DTC P02E8 Intake air position sensor cirkuit low.

Noticed that i dont get any DTC from the MAP sensor when unplugged. The MAF gives a DTC when unplugged.

 

[V70tdi]

Just a little update in positive direction.

Got help from a really nice and helpful one from the country north of US. Couldn't read out the existing tune when it was locked but got a stock tune that he modified to suit my truck that I flashed it with and so far everything seems good. No reduced engine power after the new flash file.

 

[Ron Nielson]

Noticed that i dont get any DTC from the MAP sensor when unplugged.

Strange. Your ECM really needs this MAP information

 

[darkness]

Noticed that i dont get any DTC from the MAP sensor when unplugged. The MAF gives a DTC when unplugged.

Strange. Your ECM really needs this MAP information

Unplug you barometric pressure sensor and see what happens. I wonder if you have the plugs reversed? They are the same.

 

[V70tdi]

Strange. Your ECM really needs this MAP information

After i got the new tuningfile loaded i get all codes and CEL working'. Dont know how the previous owner tuned it but it was not good at all.
I got the reduced engine power back today but it was easy solved when i now can read the codes and it showed faulty accelerator signals so I digged in to that and found a speed limiter box wired in to the accelerator and speed signal. Rewired it back to original and after that i dont got any kind of CEL or codes so far. The speedlimiter is probably there since the old Swedish rules about hevy trucks limited to 80kmh