Fault Code P0102 - MAF Short Circuit/Open Circuit

Afternoon folks, I’m looking for some advice and next steps on where to troubleshoot the MAF fault appearing. Considering buying a new sensor but just want to be 100% first. Symptoms are hard to start and won’t idle initially, just dies if I don’t hold throttle up. If I hold the RPM up above 1.5k for a couple of minutes it eventually idles but reluctantly/lumpy. Durametric shows MAF voltage constant at 1.00v regardless of RPM. At 2k RPM the Air Mass kg/h is around 65-70 I’ve checked pin 1 & 3 resistance which is around 2.6k Ohm at 18-20c. I’ve also confirmed 12v and 5v reference on the MAF connector relevant pins. Disconnecting MAF makes no difference. Cleaned all connectors and plugs with contact cleaner and tried cleaning MAF with proper cleaner. Cleaned IACV and throttle body fully. Background is I purchased the car with suspected cylinder head fault (it also had this idle issue too according to previous owner). I have fully stripped, Inspected and rebuilt the engine, I was especially careful during rebuild with vacuum and plenum/intake connections as read lots of people get issues here. Everything is new, I replaced pretty much every part during the rebuild. Car does have K&N induction filter and from the paperwork looks to have been dynoed (with HP up on standard). I also see no CAM deviation on Bank1… could this perhaps be a flashing/DME issue? I’m going to do a smoke test this week to check for vacuum leaks just in case. What else should I check? Is it an actual wiring issue (wires look ok in engine bay) or is the fault code a red herring? Car is a 1999 C2, cable throttle version. Thanks in advance.

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Is the air mass reading in kg/hr going up and down if you rev it from tickover to say 2000 rpm? 70 at 2k rpm suggests it is, it should be around 16- 20 kg/hr at tick over. I've got a 996 turbo, here are some readings from mine with a new maf just fitted. Not saying yours should be the same as below but it should give a rough idea what yours should do! -Tick over at about 50'c water temp 27kg/hr and 1.35v -As above but 2700 rpm 70 kg/hr and 2.00 v -Ignition on, engine off 1.01v Don't know why your maf voltage is staying at 1.0v especially if your kg/hr reading does go up when you rev it?! Mac

P0102 code - Rennlist - Porsche Discussion Forums 996 Forum - P0102 code - This issue started when we connected a Durametric to a 1998 996 track car and observed the P0102 code (which returns immediately when cleared). As a diagnostic aid, we swapped a MAF from the same model year Boxster (my track car) into the 996 and observed the same code... rennlist.com A very brief search for porsche p102 and this was first thing that came up, it suggests that if you have a fixed 1v it means your car is in limp mode and the kg/hr figure is generated by the ecu rather than from the maf. The variable voltage appears on pin 5 of the maf, I'd check to see if you have a steady 1v there! Mac

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I did read through the post you shared previously however it seemed they never actually got to the bottom of the problem and just kept changing MAFs until one (a cheapo one) worked. I did a few more quick tests today. Continuity from DME to MAF on all pins is good; there is no resistance either. With IGN ON / Engine Off: Checked Pin 5 - with the MAF sensor disconnected = 0v Plugged in the MAF = 0.99v measured on both Multimeter and Durametric ENGINE Running: MAF voltage never changes - regardless of RPM. Tried blowing air directly across the MAF wire - no change to voltage. IDLE kg/h = 18-22 3000rpm kg/h = 150-160 MAF voltage does not change at all regardless of speed or airflow etc. The kg/h does go up/down but seems to be very high once above idle. One other thing I noticed today - ambient temp in my garage was around 9c (engine bay temp was 8.5c according to Durametric) however the car temp indicated on the dash was reading -2c. Finally, took the car for a drive (its first since rebuild) to see if it would just 'sort itself out' which it didn't, however upon return, I noticed there was now a fuel leak (which was not there when doing the above tests) from the rail/rubber pipe connection

So if the 12v and 5v are there, and the output is definitely on pin 5 and you're getting a steady 1v (which is the output with ignition on and engine off) even when air is flowing over the maf doesn't that prove the maf is not working? And as pin 5 is an output from the maf and an input to the dme I can't see how the dme could be doing anything to keep it at 1v. Mafs are kind of a disposable part so if yours is quite old it's probably worth changing anyway. Mine had a new one at 45k then needed another at 65k albeit 10 yrs later! Are you talking about the outside temp reading -2'c if so then I'm pretty sure that's not related. Can you see the manifold intake air temp on the durametric, is that correct? Unless that is what you mean by engine bay temp, there is usually a separate sensor for this

Thanks Mac996t. Yes I’m leaning towards the sensor being at fault but I wanted to be sure before ordering one as they’re a bit pricey and already put £6.5k into my rebuild… what’s another £200 lol. I have one on order already which should be here tomorrow to test. As for temp, on Durametric as my DME is an earlier version there doesn’t seem to be the intake temp option.

Does seem like a maf fault Disclaimer if it makes no difference it's not my fault lol Have you any idea if the 2.6k ohms measured on 1 and 3 is the correct value for that temp?

I couldn’t find details of what resistance relates to what temps so I just went by another post that was 2.6k at 18-20c so I just put the MAF in my house which is at 19c I should be able to return the new MAF if no joy… keep fingers crossed

The problem is now fixed with the new Bosch MAF. IDLE kg/h = 18 IDLE MAF Voltage = 0.98 At 2000 RPM voltage increased to around 1.75-1.8v and kg/h was around 55-60. Just need to wait for the new fuel rail now