Silverado CNG Conversion

The Cavalier made me do it.

My plans were to keep my Bi-Fuel Cavalier for many years. I have spent countless hours in excessive maintenance and upkeep to ensure that it would last, however a measly part may doom my Cavalier. It is the AF-ECM (Alternative Fuels Engine Control Module). The AF-ECM is not one of GM's better designs. It has some problems and the first is it's case. It is made of aluminum and aluminum corrodes. The second problem is it's location. It is located behind the drivers side front fender skin. This makes it susceptible to weather. So when you mix the two together the seal on the AF-ECM begins to corrode. Once the corrosion begins, in time, it will force the lid apart until moisture enters and damages the unit. The current bluebook price of my Cavalier is about $2100.00 and a new AF-ECM from GM (52369822), plus reflashing the microcode, diagnostic time and tax is about $2035.00. So salvage or Ebay is the only way to go. The worst part of this story is that when people salvage bi-fuel Cavaliers for parts, they have no idea the AF-ECM is behind the left fender skin. So the part never gets salvaged and rarely makes it to EBAY. In all the years I have been scouring EBAY for Cavalier parts, I have never seen an AF-ECM. Over six years, I have replaced two AF-ECM's in my current Cavalier. Both came from local junk yard salvages. When the current AF-ECM goes, so will my relationship with Cavaliers. At that point there will be a bunch of lucky EBAY'ers who will be bidding on a ton of Cavalier CNG parts that I have collected over the years. So you are wondering what this has to do with a Silverado conversion. Well when the Cavalier goes, I am going to need a new vehicle and the Silverado is going to be it. In conclusion "The Cavalier Made Me Do It"

The existing emission controls systems have not been altered, modified or changed in any way by this conversion. This includes splicing or cutting into emissions wiring, replacing or removing any emissions components. There is no LSC (Lambda Control System), TAP (Timing Advance Processor) or any other types of emulators installed to fool the emission control systems.

Let the story begin

March 24th, 2012 by Brian McKay

Before I started this project I was toying with the idea of buying a 2013 Bi-fuel Silverado. Chevy had decided to build a factory CNG pickup and I was going to buy me one, until I saw the cost. I wanted an equipped, not stripped pickup with 4 wheel drive and the Crew Cab option. Well......... the Crew Cab was not an available option and instead of whining about the price, I realized it was way more than I wanted to pay. So the fall back plan was to buy used and convert it to CNG myself.

Based on the experience gained from my Trailblazer Conversion , I learned some valuable lessons. First lesson learned is to select your vehicle based on the ease on converting it. The Trailblazer was purchased with no consideration to the difficulty in converting it. This over sight added a major degree of difficulty to the conversion. The Silverado was purchased with the consideration of converting it to natural gas. Second lesson learned deals with CNG tank size.

  • Cavalier has 6.5 GGE in 1 tank equals 162 miles - short range.
  • Trailblazer has 13 GGE in 2 tanks equals 208 miles - medium range.
  • Silverado has 25 GGE in 2 tanks equals 400 miles - long range.

Do you see where I am going here. Install the largest tank capacity you can. A dinky little tank will make you unhappy in the end. You will feel as if you are always refueling your vehicle and that feeling sucks.