Wideband Oxygen Sensor System & Exhaust Gas Temperature Probe Installation
by Ed Bon
I have a 2002 Corvette coupe with various mods that I've been adding pretty regularly for the past 3+ years. Some of the more significant mods include heads/cam, headers, cold-air intake, 4.10 gears, wheels and tires and suspension. With the recent advent of more capable tuning/scanning packages, I decided it was time to upgrade my software and add a wideband O2 sensor to take advantage of the built-in air/fuel ratio logging capability included in the new version of the software.
This is the controller - it's just a bit larger than a deck of playing cards.
The Air/Fuel (A/F) gauge. I planned to make a minor change in it's appearance to better match my existing instrument gauges.
This is the Bosch LSU4.2 wideband O2 sensor that is to be installed in the header.
I decided that, since I was removing my header for the WBO2 installation, I might as well add an exhaust gas temperature (EGT) probe while I was at it. I found this Model 114653 1/4" Street Probe kit on Stewart-Warner's web site. It comes with it's own adapters and mounting hardware.
A close-up of the probe. It appears to be a high- quality unit. The thermocouple itself is a K-type and can be ordered with an optional gauge.
The first order of business was to remove the passenger-side header in order to have the WBO2 and EGT bungs welded in.
I had the bungs welded in at a local performance exhaust shop. I gave careful instructions because the position and angle of the sensors was critical if they were to fit into the confined spaces around the header.
In particular, the WBO2 sensor should be positioned at least 24" from the engine with it's distal tip pointing downward to prevent buildup of corrosion due to condensation.
The EGT probe needs to be positioned in the main 2/3's of the exhaust path. I was careful to ensure there was no interference of any of the sensors to the operation of the others.
I then reinstalled the header. You can see that the WBO2 sensor is located just underneath the starter motor.
I wrapped the sensor harnesses and the starter motor with Thermatec heat shielding. It's self-adhesive, reflects up to 90% of radiant heat and can withstand temperatures up to 2000 deg. F. It's also very easy to cut to shape with scissors and is simple to apply.
A worm's eyeview of the EGT probe protruding from the header. You can see the shielded harness leading up towards the cabin.
With the engine bay tasks completed, I moved into the cabin to complete the installation. First I removed the center console, the instrument panel trim, the driver's knee bolster and the driver's A-pillar trim. I then snaked a fishtape down and foward through the torque tube tunnel, attached the sensor harnesses and pulled them into the cabin. Note: For trim removal instructions, use the steps outlined in my Hurst shifter tutorial at Hurst Install
This was the area under the steering column I planned to route the gauge harness through to connect to the controller.
I ordered this gauge pod from Autometer - probably the best one for the C5 on the market.
Below is a shot of the pod next to the stock A-pillar trim. The pod fits over the stock trim and is attached using plastic push pins through holes you drill in both after laying the pod over the trim piece. The gauges are installed in the pod before it's permanently attached and then the whole assembly is snapped back into place on the A-pillar.
I installed the A/F gauge and pulled my existing shift light into the lower position before attaching the pod to the trim piece.
I then routed the harness down around the outboard side of the dash and through to the passenger footwell in preparation for splicing in with the controller. Finally, I snapped the entire pod and trim set into the A-pillar. You can see the A/F gauge and the shift light with it's protective blue cap.
Before moving on to the final wiring, I did a quick power-up test of the system to ensure it was working properly. Note that the A/F gauge is lit up.
Next, I installed the controller into the glove box and pulled the harnesses through an existing hole after popping out the plastic plug. I used Velcro to secure the controller to the bottom of the glove box. To provide power to the system, I tapped into the passenger footwell fuse panel using a Littelfuse Add-A-Circuit which piggy-backs off of an existing fuse position for auxillary accessories that can draw up to 10 amps. Here's a link to another web page I created detailing the installation of the Add-A-Circuit. Minifuse Installation
These are a few custom pieces I designed and had machined. They are, from left to right, a Delrin cover cap for the A/F gauge, an anodized aluminum gauge bezel to better match the look of the existing instruments and a Delrin mount for the shift light.
Below is the gauge pod with the shift light installed in it's mount and the A/F gauge with it's cap in place. The reason for the cap is to prevent distraction from the constantly bright, active gauge display at night and during periods when such info is not required. The cap slips on and off easily but is quite secure.
A shot of the A/F gauge in the pod before applying the gauge bezel. Note the stark contrast of it's trim ring when compared to the rest of the instruments.
A close-up of the gauge pod with the new A/F gauge bezel in place.
I tied up the wiring harnesses, secured them in place within the tunnel and connected the system to switched power in the fuse panel in the passenger footwell. I then reinstalled the trim panels. After measuring and drilling an access hole for the harnesses in the console, I replaced that as well. Below you can see the tidy wire loom and connectors in the console.
The EFI Live Flashscan scanning module fits neatly in place with the WBO2 and EGT connectors attached.
The EFI Live Flashscan scanning module cable snakes unobstructed between the console base and it's lid towards the OBDII connector under the steering column. The system works extremely well and is unobtrusive.
This is the M-250 wideband oxygen sensor (WBO2) kit I bought from PLX Devices.
Key features of the system:
Works with standalone engine management systems.
Accurate Air/Fuel Ratio <0.1, Fast Reaction
Advanced Sensor Self Calibration Circuitry. No manual calibration required.
Wideband LINEAR Analog Output (0-5V)
Narrowband Analog Output (0-1V)
Replace your stock Narrowband sensor.
32 MHz Advanced DSP Technology
Built in Resettable Fuse (No external fuse needed)
Sensor soft start circuitry, prolongs O2 sensor life.
Compact and Professional Design
"Plug and Play" Installation
ISO 9002 Certified Assembly
My scanning/tuning software is EFI Live Flashscan, currently version 7.1.7. The module includes a 3-wire port for A/F ratio logging and a 0-5V 2-wire, cold-junction compensated port capable of accepting K-type thermocouple input. Here is what is included in the kit.
It's a feature-rich package that integrates scanning and tuning capabilities into a compact configuration.
This self-contained module allows OBDII logging without the necessity of bringing a laptop along.
Pictured below are the two input ports built into the module - the thermocouple receptacle on the left and the wideband oxygen sensor input on the right.