Voltage at MAF plug?

Hi all,

I'm having trouble with high CO levels. Had the car (1995 P38, 4.6 HSE) on the scanner and I'm getting very irratic readings from the MAF sensor.

Sometimes it's correct. Testbook shows 21ish kg at idle, which increases to 70ish at 3000 rpm. However, sometimes the reading just goes dead and the exhaust emissions are obviously way out.

I've been checking wiring. On the GEMS system the car has, plug C531 (MAF connection), has three wires, a brown/orange in pin1, blue/green in pin2 and red/black at pin3. Pin3 is the earth and I've confirmed this is ok by doing a continuity check with the battery negative. Pin2 is the input to the ECM, which as far as I can tell, is correct. Pin1 is the power feed to the MAF. This comes (via a couple of 'splices') from the fusebox, connector C508, which is in turn fed by fuse 37.

Should I therefore see 12v at pin1 at the MAF with the engine running? And even with just the ignition on? And if there is a problem with this supply, could I bypass it with another feed for testing purposes?

I'm suspecting the fusebox connections at present.

Many thanks

jts change it there is no adjustment to be made very coman to fail avoid the cheap stuff on ebay

Do they fail intermitently then? I just want to make sure I'm fixing the actual problem instead of just throwing (more) new parts at it. The wiring is so thin on these.. and quite brittle when it's exposed to heat :doh:

i had one that when tested with my testbook ran faultlessly then suddenly changed to a pig all the time when switched to gas ran perfect but the gas sends a duff signal to the ecu distorting the afm signal changed the afm all was well

Thanks for your advice, I've been looking at the Bosch-branded ones from ECP. Been quoted £122+ vat, any good?

not used them but please let me know as i'm after a good source other than land rover ouch!

Too true... LR quoted £821!! :doh:

yeah not good!