“I can probably count on two hands the number of times a fuel tank pressure sensor was actually faulty.”

While that might be the case for John Forro, but he explained a number of ways to address multiple issues in his class “Evaporative Emissions” during CARS’ morning class session on Wednesday.

“There a lot of connection problems that could cause not accurate readings with the fuel tank pressure sensor. So that’s not a problem I have seen,” he states.

The only job for a fuel tank pressure sensor is to sit on top of a gas tank assembly, Forro says. It acts as a two-bar MAP sensor. It measures available pressure vacuum in a tank. The PCM uses this signal to determine if a leak is present or not.

Though theses sensors rarely are the causes, says Forro, there are easy and quick ways to test for this.

If it takes too long to build pressure, you can set small leak codes. “They’re probably more popular than large leak codes,” he notes. “A large lead code would be easier to diagnose, but smaller leak codes are more popular.”

The only disadvantage is that this sensor is on top of the gas tank, so it’s harder to get access. You can back-end around it with the PCM, though, according to Forro.