So I was trying to diagnose a low power condition on my 04 F250 when I decided to hook up my new Auto Enginuity scanner. No codes were found. When working the turbo I decided to try setting the turbo to open and closed via the AE tool and see if I could see a response from the turbo. I got no noticeable reaction from any thing. So I hooked up my O-scope to the wire to the turbo VGT solenoid and found a solid 12 volts not the variable pulse width square wave I expected. I noticed some noise on the 12 volts that I could make go away when I set the duty cycle to 0 and got noise to return when I set it for 85%. This looks to me like a blown out put driver in the control module. I took a quick look for bad wiring to see if it was shorted to power some place but I have no idea were the common chafing locations are.

1. Am I on the right track here? Any input would be appreciated.

2. I have no wiring diagrams. Need to get some. Is the turbo controlled by the PCM or the FICM?

3. Can I change the PCM myself? I assume it will need to go through firmware update and maybe some form of learn procedure that I may need dealer help with. Perhaps I can do that stuff.

Thank you all in advance this forum is a wealth of good info.

 

When you set it to zero, did you still measure 12V? Also, are you measuring the differential between the two VGT wires, or to ground?

You can replace the PCM yourself, but I would definitely make sure that's the cause first. You'll have to get a new one flashed to your vehicle so it has the correct VIN information in it. I have a second PCM from an early '03 that I am keeping as a backup. It ran with it fine, but the VIN information it holds is not correct.

 

Yes I get 12 volts regardless of how I set it with the AE scan tool. I was measuring the control wire referenced to battery ground, not the solenoid return wire. I believe these 2 grounds (sensor ground and chassis ground) are tied together. Sensor ground is derived in the PCM from its chassis ground connection. Should I see a difference here?

 

Measure between the two wires. There's a good chance the control is isolated from ground. Also, measure with it plugged in if possible; it could be floating or tied to positive, so without the solenoid pulling it down the output will float up to 12V.

 

Will do. I was measuring with the connector on by piercing the insulation and recovering with electrical tape. I only wanted to pierce one wire, but if it may make a difference I will access the return wire as well.

 

Yup. That made a difference all right. I got a square wave this time. It was all jittery and did not seem to have a consistant pulse width. My scope was triggering OK and I double checked my probe connections to be good and stable. When I commanded to 0% I got a good flat line and when I set it to 85% I got nice large square pulses. They just did not seem to all be the same size. With the PCM in control I would expect variation but when I ask for 85% I should get a real steady display on the scope with pulses the same from pulse to pulse to pulse.

Perhaps since I see a signal I should be barking up another tree. I only seem to get about 10 PSI boost according to the AE data logs I took while driving, and she just feels like a pig. I just had her out in the mountains a few days ago and felt like I could have ran faster.

 

check epb, map and baro @ koeo.
check for exhaust and intake leaks.

 

I have been looking for the EBP sensor in the AE scan tool software. I found the MAP and BARO readings easily and they are equal with KOEO. I do have a small exhaust leak at the turbo to down pipe connection post turbine. Being post turbo I did not think this would make a difference but I've been wrong before. All intake connections look solid.

 

by down pipe you are refering to the 3" outlet pipe? if so a leak on that pipe wont make that big of a differance.

 

Yup goes down to the CAT. What kind of boost numbers should I see during flat out acceleration? I have been figuring boost by subtracting BARO PSI from MAP PSI. I will look to see if I can find the EBP on the AE tool again tonight.

You know she also kind of surges a bit. Just enough to hear at idle. Don't know if this might apply.

 

disconnect the ebp and see if the serge goes away. if so suspect vgt and or connector failed.
ae might have it listed as ebpa or eb as well. I dont use ae so not a lot of help there.