Dual Wideband AFR Meter Installation

[2000StreetRod]

At some point during the installation of my M90 supercharger my AutoMeter 5978 wideband air/fuel ratio (AFR) meter quit working properly. At first I thought the O2 sensor had gone bad since the meter was indicating the maximum AFR of 16:1. I purchased a replacement sensor on ebay that included the entire wiring harness from the sensor to the meter. Unfortunately, replacing the O2 sensor did not fix the problem. I tested all of the wires from connector to connector for continuity and shorts and found no problems so I purchased another complete system. Then I replaced the old meter with the new meter and had the same symptoms. I concluded that I had damaged the wiring when installing the boost gauge, oil pressure gauge, electronic fuel pressure regulator or throttle cable. I decided to start over from scratch assuming I had two good meters, two good wiring harnesses and three good wideband O2 sensors. I purchased a dash mount two gauge pod to house left and right bank meters and removed the dash mount one gauge pod containing the oil pressure gauge which will be moved to the pillar pod where the left bank AFR meter was.

When my high flow exhaust system was installed I had the shop install a bung for a wideband sensor on both banks. The left bank wideband O2 sensor is shown below - downstream of the pre-cat narrowband O2 sensor.

That was done in June 2013 and there has been a plug in the right bank ever since which did not want to come out. I have a set of hex head sockets but there was no room for a drive to use them. The only thing that would fit was a short allen wrench. Every day I soaked the plug with PB Blaster and "tapped" the end of the allen wrench several times with a length of pipe struck by my 4 lb hand sledge. On the third day it broke loose and I was able to install the new wideband sensor identified below.

The post-cat O2 sensors were replaced with short cable units by a previous owner. The right one did not reach the mounting bracket so I tie wrapped it next to the left one and attached the wideband connector to the unused mounting bracket.

I drilled a 3/4 inch diameter hole in the transmission tunnel between the reinforcement ridges to allow pass thru of the smaller connector that goes to the meter.

I found a grommet that fit the hole and enlarged the center with a file for the two gray cables. After passing the cables thru the hole and installing the grommet I installed wire looms to protect the cables.

The various colored wires on the left are for power, datalogging and peak AFR detection.

 

[2000StreetRod]

Cable routing

The loom I installed shown below contains the two wideband sensor cables and three other wires that are routed below the carpet and aft. The red wire goes to the center console switch to disable the pre-oiler for occasions when the ignition is on but the engine is not going to be started for a few minutes or longer. The blue and brown wires go to another to be added console switch that prevents the PCM from energizing the A/C compressor for all HVAC mode selector switch positions.

I plan to force sealant into the spaces in the center of the grommet to keep out moisture and road grime.

The excess lengths of sensor cables are coiled behind the HVAC controls and below the radio slide mount.

I used a Dremel with a small grinding stone to make a hole in the underside of the dash large enough for the meter connectors to pass thru.

I cut a similar hole in the top of the dash with a knife.

I routed the sensor cables and meter wires upward to the holes in the dash.

I installed another loom just for the individual meter wires (power, ground, peak AFR & datalog) since they are connected in an accessible location.

 

[2000StreetRod]

Cable routing (continued)

The loom for the individual meter wires (power, ground, peak AFR & datalog) goes to behind the metal support plate & above the hood release.

Each pair of datalog wires (blue ones in photo) will have a 2 pin connector. I'll replace the 4 pin connector on the X3 PowerFlash cable with two 2 pin connectors. That way I can record any two of Bank1 AFR, Bank2 AFR or injector delta pressure.

I forced RTV Blue into the open spaces in the floor grommet and then secured the wires to the floor with duct tape.

The tape keeps the wires in place (I plan to eventually install new carpet) and gives the wires additional protection.

 

[2000StreetRod]

Dash pod

I pulled the meter connectors & wires up thru the dash opening.

The top of the dash is curved and the bottom of the dash pod is flat. It doesn't show in the photo but there is about a 1/4 inch gap between the front corners of the pod and the dash.

I will trim the front of the pod to match the dash which will also slightly decrease the undesirable tilt of the gauges. There are three mounting holes in the pod - one on each side and one in center back. I've learned from experience that it is very difficult with the windshield in place to drill a hole in the hard plastic that supports the dash foam. I will attempt to melt a hole by heating a bit with my propane torch.