1G 2G MAF in a 1G Wiring Problem

[mac 108]

I have a 90 AWD that has a 2G MAF with a 2G MAF plug soldered into the factory harness.

The car has no MAF readings.

The car previously had an SAFCII that has been disconnected.

It has been converted to a 2G blackbox ECU using a jumper harness.

For both the original 1G ECU and the 2G ECU, I am getting codes for a bad MAF/no MAF readings from any of the three sensors.

1G ECU shows codes 12, 13, and 25
2G ECU shows codes P0110, P0100, P1500, and P0105

I have tried two different 2G MAFs with the same result so it appears that is not the issue.

I assume that there's a wiring issue either at the ECU plugs where the SAFCII was tapped in or with the wiring for the MAF connector. Because both the ECUs are showing the same codes, I assume that there is not an issue with my 2G ECU jumper harness.

None of the wires are obviously damaged. Everything appears to be in good condition.

What would be the first step in diagnosing the problem?

 

[onefast2gdsm]

make sure your jumper harness is getting a good connection. When I put mine in it wasnt getting a connection at one of the plugs so I hardwired the 2g plugs.

 

[91stocker]

Heres a nice write up you can go over to make sure the wiring is correct.

http://my.prostreetonline.com/2015/02/23/how-to-wire-a-2g-maf-in-a-1g/

 

[steve]

You have 1G Fault codes of:
12 = Air Flow Sensor
13 = Intake Air Temp Sensor
25 = Barometric Pressure Sensor

The most common cause for all three is a bad sensor ground connection but also check for the +12v and +5v power at the 2G MAF connector with the key on.

Here's the wiring that has worked to compare to:

Pin 1 on the 2G connector goes to the green/red wire that was pin 4 on the 1G harness.
Pin 2 on the 2G connector goes to the green/yellow wire that was pin 7 on the 1G harness.
Pin 3 on the 2G connector goes to the green/blue wire that was pin 2 on the 1G harness.
Pin 4 on the 2G connector goes to the red wire that was pin 3 on the 1G harness.
Pin 5 on the 2G connector goes to the green/black wire that was pin 6 on the 1G harness.
Pin 6 on the 2G connector goes to the green/orange wire that was pin 8 on the 1G harness.
Pin 7 on the 2G connector goes to the green/white wire that was pin 1 on the 1G harness.
Pin 8 on the 2G connector has nothing connected.

Here's what the 1G wiring is for:

The green/white wire in the 1G MAF harness is the MAF Reset signal. (turbo only)
The green/blue wire in the 1G MAF harness is the Airflow signal.
The red wire in the 1G MAF harness is +12v from the MPI Relay.
The green/red wire in the 1G MAF harness is the +5v sensor power.
The green/black wire in the 1G MAF harness is the sensor ground.
The green/yellow wire in the 1G MAF harness is the barometric pressure signal.
The green/orange wire in the 1G MAF harness is the air temp signal.

The SAFC intercepts the MAF Airflow signal, did you remember to reconnect the two pins (in and out) when the SAFC was removed?

 

[mac 108]

Haven't had a chance to test the wiring yet.

In the meantime, are there are any grounds that I can check that might be loose or corroded that would caused the problem?

 

[steve]

Test the power and grounds listed.

 

[mac 108]

Finally going to test the wiring today. Will post what I find.

 

[mac 108]

The wires were wrong going from the harness to the 2G maf plug. Dumb on my part. Should have checked first.