[rwoody29]

I posted a few weeks back about some fault codes been shown up on my car. I'm down to this one now! Mass air flow sensor implausible signal. The traction control and epc light both come on solid amber, they do go off if the car is driven steady. It's had a new maf last week so I'm thinking air leak could be causing this. Where are the best places to start? It's got a charger fitted if that makes any difference

 

[PaulW]

Was the MAF genuine? Have you still got the old one? Did the old one chuck up the same code?

Heres what RossTech say

16485/P0101/000257 - Mass Air Flow Sensor (G70): Implausible Signal
Possible Symptoms

• Loss of Power
• Erratic Idle

Possible Causes

• Mass Air Flow Sensor (G70) faulty
• Air Leak(s) after Mass Air Flow Sensor (G70)
• Intake Air Filter dirty/faulty
• Ground Spots corroded or Paint Residue
• Wiring and/or Connections from/to Mass Air Flow Sensor (G70) faulty

Possible Solutions

• Check Intake Air Filter
• Check Mass Air Flow Sensor (G70)
• Check Ground Spots
• Check Wiring and/or Connections from/to Mass Air Flow Sensor (G70)

Special Notes

• In MY 1995-2002 (?) in Europe at VW-diesel-cars G70 had the bad reputation of slowly losing his performance, causing loss of power. It's not a matter of defective or breaking down, but it is filthy / dirty (not easy to clean). You can check functionality by making a log in [01-engine], [meas.blocks-08], group 003 (3e gear, full throttle, from 1700-4000rpm)
• It is not uncommon for a TDI to set Implausible Signal Mass Air Flow Sensor (G70) faults when the engine performance is reduced due to a mechanical problem. These mechanical problems may include, but are not limited to:
  • Faulty electric fuel pump or Restricted fuel filter. See the Fuel Pump Basic Settings for PD, PPD, and CR TDI Enginespage for Basic Settings tips after replacement.
  • Excessive restrictions in the intake/exhaust system
  • Internal camshaft/valve/lifter problems

 

[rwoody29]

Yeah it was, it put the code up before which was why I changed it

 

[rwoody29]

As well, when on full rattle it holds back between 4-5k rpm which is when it throws the fault up so its under load that causes it

 

[PaulW]

Ahh right, what about getting the MAF mapped out completely?

You could get a garage to do a 'smoke test' to check for leaks, saying that because its pulling air its hard to find.

 

[JamesBaby]

Block 032 will tell you if it's an air leak somewhere. Post the values of the 4 boxes and ill give you some feedback.

Check the MAF wiring. Make sure you have good tight connections and that they have the proper voltages, and a good earth.

 

[rwoody29]

Thanks I look at logging that

 

[rwoody29]

Here are the readings from block 032

 

[JamesBaby]

Wow. Ok. The injector on time is being reduced because you are running way to rich. The ecu thinks the engine is using more air than it actually is. It's adding what it thinks is the right fuel, only for the O2 sensors before the cat to adjust it down by reducing the injector on time.

The first box is at idle, the second box through the rev range.

You have less air going in than is being reported. Either the MAF/wiring is sending too high a signal, MAF is faulty, or the air is leaking out after being measured. Check for leaks in the pipe work or even the manifold.

 

[rwoody29]

Brill thanks for your help so far

 

[rwoody29]

It also has a maf clamp installed as part of the supercharger kit, do you think this could have anything to Do with it?

 

[CoolHands]

I had this fault when I had my supercharger fitted - it turned out to be poor connection where the wires from the original maf had been soldered.

I don't knowif you fitted your vf yourself or not - but the wires are extended and sodlered to the original harness. That was where the problem was. The OE wires are very thin. I would suggest you (if you're good & careful) or an expert who you trust, re-soldering the connections (they may have even been connected using some kind of clips which will give a poor connect). The original VF supplied ones (shown in the pics) are what caused my problem. I sodlered them properly to fix it.

Hope that helps.

these ones

 

[rwoody29]

Thanks for the reply, it's back in with psi tuning who fitted the kit but I suspect you're right that its a wiring fault to the maf that's causing the issue

 

[rwoody29]

Spoken to the garage today and they say its running rich on idle and lean on full throttle. Maf and boost readings are good, so what could be driving this?

 

[CoolHands]

Either the MAF/wiring is sending too high a signal, MAF is faulty, or the air is leaking out after being measured. Check for leaks in the pipe work or even the manifold.

as above - maf; wiring; pipework.

IMO the wiring (as described by my own experience) is the most likely culprit baring in mind you say the maf has already been changed thus ruling that out, and the pipework should be easy for them to visually check.

 

[rwoody29]

Did you have the maf clamp? This has got one on

 

[CoolHands]

errrr... dont know. wassit look like??!!

 

[rwoody29]

It's a little black box that goes into the wiring to the maf

 

[rwoody29]

Had the car back today as its been in the garage for 3 weeks... They are a little lost as to what is wrong with it! The maf has an occasional voltage spike which is throwing the error codes up. Maf has been changed again, wiring all checked, no air leaks, boost is strong, fuelling been checked. They have run out of ideas, so anyone else got any????

 

[JamesBaby]

If you truly have checked the wiring back to the ecu it would point to a faulty ecu IMO.

I would re-wire the entire MAF wiring back to the ecu itself prior to digging out the ecu.

BTW, When you clear codes, run a full auto scan and clear all DTCs. This will ensure all modules are cleared as the fault you describe can also be logged in the abs control ecu. (I know because I had this fault a few months ago)