I got codes p0440 & p0452 on my 2000 Blazer S10. I've been reading the countless threads on the EVAP problems. I'm going to do all the visual inspections. But soon I will be dropping my fuel tank to get to the fuel tank pressure sensor. I want to test the sensor before I go out and spend the $40. I don't own a scan tool nor can I afford one. But I do own a digital multi-meter. I've read you can do some diagnostics on this part with a multi-meter. But I've read you can do some damage to the ECM in that process. Can anybody help me on what not to do in diagnosing this part using a digital multi -meter? and while we are at it, how to diagnose my fuel tank pressure sensor and the electrical connection using a digital multi-meter?

Thanks!

 

DTC's must be diagnosed & repaired in the order they are retrieved. The first DTC can, and usually does, cause other DTC's to set after it, meaning that any subsequent DTC's could very well be false. P0440 indicates there's a problem with the EVAP system. This might be a blessing in disguise from the aspect of, it's probably not an electrical problem and likely there is a vapor leak in the system. When the PCM runs the EVAP monitor, it applies a given amount of vacuum to the fuel tank. Then it seals the system and monitors the fuel tank pressure sensor for the vacuum to decay. If it decays too rapidly, there's a leak in the system and the DTC sets.

The most common cause is a poor seal at the fuel cap, but could be any one or more of several things:

* A disconnected or malfunctioning fuel tank pressure sensor
* A missing, malfunctioning, improperly installed, or loose fuel cap
* A disconnected, damaged, pinched, or blocked EVAP purge line
* A disconnected or damaged EVAP vent hose
* A disconnected, damaged, pinched, or blocked fuel tank vapor line
* A disconnected or malfunctioning EVAP purge solenoid
* A disconnected or malfunctioning EVAP vent solenoid
* An open ignition feed circuit to the EVAP vent or purge solenoid
* A damaged EVAP canister
* A leaking fuel sender assembly O-ring
* A leaking fuel tank or fuel filler neck

This link will help in diagnosing the problem: https://blazerforum.com/forum/diagno...plained-35145/