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Discussion Starter #1 (Edited)
Trying to help a friend bring his 2004 VR back to life. This is how he got the car so we are trying to fix it.

The car starts and runs ok. If I drive it it goes into limp mode. This induces the Reduced Engine Performance and Engine System Service Required messages. After I clear all codes the messages are gone I am getting a lot of codes but the ones of interest are:

ECM-1300 Mass air flow (MAF) sensor. Flow too low. Permanent fault
ECM-1600 Boost pressure sensor. Signal too high
ECM-170F Atmospheric pressure sensor / boost pressure sensor range check. Faulty signal
ECM-2100 Fuel pressure sensor. Signal too low
ECM-211A Fuel pressure. Signal too low
ECM-5600 Oil level sensor. Signal too high
ECM-913C Throttle unit. Faulty signal
ECM-9530 Accelerator pedal (AP) position sensor, digital signal. Signal too low

And last but not least, I have narrowed it down to this:

ECM-8410 5 volt power supply. Signal too low

What VIDA says about it:

Condition
Diagnostic trouble code (DTC) ECM-8410 is stored if the 5 volt supply circuit for the mass air flow (MAF) sensor, boost pressure sensor, air conditioning (A/C) pressure sensor, oil level sensor and fuel tank pressure sensor has a voltage higher than 6 V (high signal) or lower than 4 V (low signal) and the control module interprets it as a fault.

bla bla bla

Signal too low:
short-circuit to ground in the 5 volt supply cable
Defective mass air flow (MAF) sensor
Defective boost pressure sensor
Defective air conditioning (A/C) pressure sensor
Defective oil level sensor
Defective fuel pressure sensor.
The 5V supplies the above 5 sensors and originates form the ECU. I see some voltage with car in position II (~1.8V). Once I start it I see 0V. Tried unplugging the sensors one by one and nothing.

Tried my '04 R and I see the 5V. Bad ECU?
Has anyone fixed limp mode problems before?
Anything related to the 5V supply voltage for the sensors listed above?
 

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Unplug your ECU and ETM, make sure your connections aren't corroded/green. Spray some contact cleaner on the receiver for both (make sure it's electronics safe/purposed) and plug them back in. Maybe try plugging/unplugging a few times.
Also, make sure the battery is connected well and fresh.
 

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Also, start looking for a break in the wire harness if that doesn't help. Check grounds in engine compartment. Was this car ever hit?
 

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check your fuses in all of the fuse box compartments...probably a major relay switch went out or something...
 

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Discussion Starter #6
Unplug your ECU and ETM, make sure your connections aren't corroded/green. Spray some contact cleaner on the receiver for both (make sure it's electronics safe/purposed) and plug them back in. Maybe try plugging/unplugging a few times.
Also, make sure the battery is connected well and fresh.
It has no ETM. 6-speeder. The contacts look good. I don't see any copper oxidation. I have also plugged it in a few times.

Also, start looking for a break in the wire harness if that doesn't help. Check grounds in engine compartment. Was this car ever hit?
I will check the grounds later. Haven't done that yet. The car was hit in the front right and ripped some headlight/turn signal wires. Fixed these and all is working.

check your fuses in all of the fuse box compartments...probably a major relay switch went out or something...
I checked all fuses but need to check all relays. That I haven't done.

New battery.
I have a charger plugged in at all times, one of the big professional ones. Car fires up fromt he first time.

Looks like the 5V is not coming from the ECU.
 

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These cars are very sensitive to the battery and do weird things when it starts dying, even if the car starts and runs fine. A lot of people on here have seen lots of CELs for a bunch of different things pop up at once and it was the battery. It wouldn't hurt to try switching it if it is the original or you don't know when it was last replaced.
 

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Discussion Starter #8 (Edited)
Solved! The ECU is not supplying 5V. I supplied 5V using a resistor from the positive terminal and all codes went away. The ECU has a 5V variable that I monitored in VIDA, once I hooked up my external 5V supply it read the voltage. No more Engine System Service Required or Reduced Engine Performance. I also had a gas pedal fuse blown, that caused me another hour of headaches. If gas pedal has problems it produces instantaneous reduced engine performance. Test drove and the sucker pulls hard. :)
 

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Solved! The ECU is not supplying 5V. I supplied 5V using a resistor from the positive terminal and all codes went away. The ECU has a 5V variable that I monitored in VIDA, once I hooked up my external 5V supply it read the voltage. No more Engine System Service Required or Reduced Engine Performance. I also had a gas pedal fuse blown, that caused me another hour of headaches. If gas pedal has problems it produces instantaneous reduced engine performance. Test drove and the sucker pulls hard. :)
wow.. where is the gas pedal fuse?
 

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Discussion Starter #11 (Edited)
Are you now permanently supplying an external 5V?
I have to. By external I mean external to the ECU. I am pulling 12V from the jumper terminal and using a resistor to bring it down to 5V. Either that or $1000+ for a new ECU. I'm going to measure the current and ensure I have the proper resistor, don't want it to overheat. I drove around in my SR for a about 25 minutes monitoring the 5V supply. I plotted it and it is stable b/w 5.19 and 5.21V. All five sensors require constant 5V, I am concluding this is switched 5V supply. On the VR (car with problem) the ECU even sees the voltage that I pushed in.

wow.. where is the gas pedal fuse?
Yup, it is in the front left engine compartment fuse box. Fuse 8 or 9, can't remember exactly. The gas pedal is pretty complex, there are over 5 parameters I believe that I monitored. Both analog and digital signals come out. It is drive by wire and the connector has 4 wires.

Edit: Using switched 5V now, not battery terminal, that would drain the battery overnight.
 

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were are these???---Unplug your ECU and ETM..
my deal on my 04 V70...
Last Sunday i changed out my bad left drive shaft. and on Wednesday Anti -Skid message in dash which i pulled the ECM fuse under hood for a few to get home..Well today i got a Anti-Skid message again and after that a brake failure stop carefully. i think in limp mode and not down shifting all the way? tonght after she has sat a while i pt my OBDII reader in and getting a p0600 code, and transmisson requires service message in dash. last Sunday i did a oil change and tranny drain and fill....
now the brake failure message i do know my brake pads are really bad and i am hoping changeing out the brakes will clear that up.
any ideas guys.... thanks!
 
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