nitehawk3600

My SES light is on and the codes are p0200 injector circuit failure and p0304 cyclinder 4 missfire. I believe the p0200 is causing the p0304 but dont know what is causing the injector problem. Could it be a electrical problem or just a dirty and stuck poppet valve on #4? The SES light is on after starting engine and then when speed gets to 30 mph the light begins to flash. Once speed drops down to 30 mph the light goes back to being solid. This very consistant pattern. With the light flashing there is defineite sluggishness to engine but not a real bad roughness. This has been happening for 5 days now. I have cleaned the MAF sensor, cleaned the EGR valve and changed the air filter. I have also put a timing light on the #4 spark plug cable and have seen no miss in the light at idle ot when reved uo. Any thoughts or help is appreciasted.

old_master

The P0200 is causing the P0304, and it's an electrical, not mechanical problem. The injection system is Central Sequential Fuel Injection, (CSFI) and uses an injector assembly with 6 mini injectors in it. The unit is serviced as an assembly, the injectors are not individually serviced. Check the circuit from the PCM to the #4 injector for battery voltage at the injector and a pulse ground while cranking. Also check for a short to ground, or possibly a shorted injector.

MT-2500

What engine?
Codes indicate a problem at no 4 injector.
Make sure plugin and wiring is good shape.
Check for injector voltage to cylinder 4 injector and plugin and for good injector pulse.

__________________
Remember proper testing gives us the answer to many problems.
MT

nitehawk3600

Its a 2001 Blazer LT with 4.3 Vortec vin code "w". I'm not very good at electrical but I do have a multimeter I have used before for with very specific directions. Is it possible to provide more detailed intructions on how to check the items that have been described or direct to where I can get more details. Does the plenum have to be removed to get to the spider unit with the poppets to check them? I dont know where the PCM is located to be able to do the testing. Any addtional instructions are appreciated. I unfortunately dont have the money right now to take it to a mechanic and need to fix it myself. Thanks

nitehawk3600

As I was checking out the wiring for the fuel injectors, I noticed the wiring harness was pretty loose and realized the harness was not snapped in secure. After securing the harness I cleared the codes and took it out for a test ride and the SES light never came on and it ran great. I have driven it about 200 miles with no problems and my mpg has gone from 14 to 17 mpg.

MT-2500

Thanks for posting back how it went.
Sounds like you found the problem.
Good luck
MT

__________________
Remember proper testing gives us the answer to many problems.
MT

old_master

Nice job MT, you hit the nail right on the head!

MT-2500

Thanks Old_Master
That plugin is a little hard to get back on good.
Glad he was able to look at it and find the problem.
MT

__________________
Remember proper testing gives us the answer to many problems.
MT