Wedge AFM issues
Discussion
Learning fast about wedges with all the info out there but one problem ive not come across on any forum. 350i 4CU air flow meter, the voltage measured across terminals 6 and 7 of the ECU actually increases as the flapper is opened from 0.5 to 2.7, Understand it should decrease from 3.7 down to 1.6. Inside the case all looks as new and all other tests as they should be except fuel pump runs continuous with ignition on but switches off when the flapper is opened. Any ideas?
The AFM is just a potentiometer and the wiper gives you the voltage from one terminal sweeping through to the other.
If the voltage at each end of the sweep is the wrong way around it will produce the effect you're observing. Most likely cause is that the loom or teminals at one connector are swapped over somehow?
What is the history of the wiring loom?
Other than that try to borrow a spare ECU and see if it does the same thing - if not there's a fault inside your ECU but it sounds like an unusual type of fault.
If the voltage at each end of the sweep is the wrong way around it will produce the effect you're observing. Most likely cause is that the loom or teminals at one connector are swapped over somehow?
What is the history of the wiring loom?
Other than that try to borrow a spare ECU and see if it does the same thing - if not there's a fault inside your ECU but it sounds like an unusual type of fault.
• Leave voltmeter -ve connected to pin 9 and move voltmeter to pin 7.
• Reading should be 3.7 ± 0.1 volts.
• If voltmeter reads low, check wiring for high resistance.
• With voltmeter still connected to pins 7 & 9, slowly open the air flap.
• Reading should gradually decrease to 1.6 ± 0.1 volts.
• If results are not within those specified above replace air flow meter.
• If OK, refit . this is the correct test. instructions from sd1 site think your reading from wrong pin
If the loom is original then I wouldn't start swapping connectors over right now. All the same it would be worth checking with a multimeter end-end that the connections match up at the AFM multiplug and ECU multiplug (to confirm the colours). Then you can take a view on what to do next.
Might also be worth cleaning all the earths...the 3 main ones at least....
1. N/S front suspension turret
2. Top of rear N/S rocker cover
3. One just below that one...this one is for ECU.
I would also check and clean the connections..including the black and white wire (Bullet connector) from distributor to AFM/ECU.
It also worth removing the ECU plug and cleaning up the male & Female connections...But make sure you give it a good firm push until it clicks back on.
Hope this helps
Ziga
1. N/S front suspension turret
2. Top of rear N/S rocker cover
3. One just below that one...this one is for ECU.
I would also check and clean the connections..including the black and white wire (Bullet connector) from distributor to AFM/ECU.
It also worth removing the ECU plug and cleaning up the male & Female connections...But make sure you give it a good firm push until it clicks back on.
Hope this helps
Ziga
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