IAT and MAF

[ovlov440]

Hi

First post on this forum so please be gentle!

Friend of mine has a 2005 Berlingo 2.0 HDi. Her alternator failed so a mate and I replaced it with a new 150amp unit.

2 days later her engine management light popped up on the dash and the engine went into 'limp home' mode. My OBD reader would not connect to the Berlingo computer so it went to a local garage to be read.

The codes it came back with were:

P1352 - Glow Relay - Short circuit or defective
P0113 - IAT sensor - open cicruit/positive short
P0102 - Air mass-meter signal - open circuit/earth short

Putting aside the glow relay as the cause (as I believe this would not cause a limp-home problem) I concentrated on the other 2 codes. Finding the IAT and MAF were integrated into one unit I tested the 5 wires at the plug and got what I believe to be the correct readings - 5v/12v/earth/0v/0v. This lead myself and a mate (who is an electronics tech for the RAF) to concluded that the MAF/IAT was faulty and ordered a new one.

The new unit arrived and was fitted. Starting the car, the dash beeped and the 'Check Engine' light went out. Left it idling for 5 minutes then took it for a test drive. 5 minutes into the test drive the dash beeped, the light came on and the engine went into limp mode. 10 seconds later, another beep, the light goes out and full power is restored. 30 seconds later, beep - light - limp mode.

I then removed a known working MAF/IAT from a Peugeot Partner and put it in the Berlingo. The light would not go out. As a double check I then put the Berlingo MAF into the Partner and it drives all ok - no light.

Therefore, if the new MAF/IAT is ok, all the voltages/earths at the plug are ok and the air filter, air box and rubber hose from the airbox are all ok what on earth is the issue. I am out of ideas and would appreciate any help/ideas.

Ta

Ade

[crickleymal]

Does it go into limp home mode when the engine is over a certain rpm? Or is it random?

[Ol'Jeffers]

I think I'd be checking the wiring loom for chafing causing random earths/shorts or
wires broken at their terminations, which won't be visible due to the insulation
being intact.

[ovlov440]

ok - so following on from the original post here is the continuation of the story....

I have verified the ground, 5v input and 12v input on the plug that connects to the IAT/MAF

I have also run a continuity check on the two signal returns that go from the plug back to the ECU. All are ok (even when moving the cable around there is no drop in the signal).

What I have noticed is that there are a large number of bubbles visible in one of the clear pipes from the fuel filter - from the direction of travel i would say it is the pipe that connects the fuel filter to the engine. Using the priming bulb that appears to have cleared that (at least temporarily) and when starting the engine again the 'check light' went out, only to reappear after 2-3 mins at idle.

VERY confused now - all the wiring appears to be ok, new MAF/IAT fitted and yet still get limp mode/check engine light

ARRGGHHHH!!

[ron]

ok - so following on from the original post here is the continuation of the story....

I have verified the ground, 5v input and 12v input on the plug that connects to the IAT/MAF

I have also run a continuity check on the two signal returns that go from the plug back to the ECU. All are ok (even when moving the cable around there is no drop in the signal).

What I have noticed is that there are a large number of bubbles visible in one of the clear pipes from the fuel filter - from the direction of travel i would say it is the pipe that connects the fuel filter to the engine. Using the priming bulb that appears to have cleared that (at least temporarily) and when starting the engine again the 'check light' went out, only to reappear after 2-3 mins at idle.

VERY confused now - all the wiring appears to be ok, new MAF/IAT fitted and yet still get limp mode/check engine light

ARRGGHHHH!!

You need to hail Rustcrat or Addo pretty loud.Good luck.:thumbsup: