P0401 and P0441 results on 95 Jimmy

[sail978]

Did a OBD test because the 'service engine soon' light is coming on and off. Can anyone tell me what it means and how it can be fixed? Thanks.

[old_master]

P0401 is "EGR flow insufficient". This could be any one or more of several things ranging from a restricted passage in the cylinder head or intake manifold to a faulty EGR valve, to a control circuit fault.

P0441 is "EVAP Emission Control System Purge Flow Fault". This DTC could be any one or more of several things also. Possibilities range from a faulty purge or vent solenoid to a restricted line that connects the fuel tank, purge canister, vent solenoid and purge solenoid together, or a fault in the circuits that control the solenoids.

The possibility also exists that one of these codes is triggering the other to come on. If you don't have access to the diagnostic flow charts for OBDII, It would be best to have a certified driveability technician at least diagnose it for you, if not repair it also.

[sail978]

Thanks for the info. Took it to the mechanic. He got the P0401 situation fixed. Thought he had both figured out but after driving the truck a couple of miles, the SES light comes back on and only shows P0441. Happens every time you start the truck - no light and then a couple of miles, the SES light comes on. Any ideas?

[old_master]

The EVAP monitor usually takes longer to complete than a couple of miles. If the SES light is coming on that soon, I would suspect a "hard fault", in other words, a problem the PCM is "seeing" before it completes the monitor. The EVAP system includes the canister purge solenoid which is in the intake manifold, a vent solenoid near the purge canister, the tank pressure sensor on the top of the fuel tank, and of course the wiring to connect it all to the PCM. It is more than likely one of those items as the monitor needs to run before the PCM can determine a problem with the systems ability to hold pressure.

[sail978]

Thanks for replying Old Master. Update - My kid drives the truck yesterday. Starts out fine and then all of a sudden the engine starts shaking and stalling. Goes back to the mechanic. They replaced the EGR valve that was stuck open and not working. Supposedly everything is working now. He took it for a 10 miles spin and is going to drive it again tomorrow. I'm hoping this will resolve the problem. He replaced something else on the P441 code (bad cell phone connection) but I'll get more info when I'm picking up the truck and will report back.

[old_master]

Replacing the EGR valve could explain the stalling and the P0401, and also why the SES light came on so soon before, (EGR is one of the first monitors to complete). If the problem continues, cleaning the EGR passages in the cylinder heads and intake manifold along with the installation of an EGR gasket with a screen built into it, may be necessary to asure a long term repair.

[sail978]

Well, we thought we were home free. New EGR valve and the mechanic drove it yesterday without any problem. Picked it up tonight and drove about five miles and the SES light comes on again. Repair shop is closed so my son takes it Advanced Auto and does a scan - P0441 again (at least no P0401). So now I'm thinking there's something else going on not related to the 401 - could be one of the parts you mentioned old master? Should I go out and purchase a new gas cap just to see if that's the problem? Thanks for all your help.

[old_master]

P0441 is "EVAP Emission Control System Purge Flow Fault". This DTC could be any one or more of several things. Possibilities range from a faulty canister purge solenoid, canister vent solenoid, restricted line that connects the fuel tank, purge canister, vent solenoid and purge solenoid together, or a fault in the circuits that control the solenoids. A faulty filler cap would put in a code indicating a leak in the EVAP system. We're looking for a flow problem. Something is restricting the flow of fuel vapor to the intake manifold from the purge canister. Always start with a good visual inspection. Start with the line from the purge control solenoid, located on the passenger side of the intake manifold, to the purge canister, located in the left rear 1/4 panel behind the tire. Remove both ends of the line, you should be able to blow through it very easily. Next, if you plug one end, the line should hold vacuum. You are checking the integrity of the line both for the ability to flow, and also not to leak.

[drdd]

Originally Posted by sail978

Did a OBD test because the 'service engine soon' light is coming on and off. Can anyone tell me what it means and how it can be fixed? Thanks.

do you have CPI ?

if so, have you ever replaced the CPI and nut-kit ?

[sail978]

Well, Jimmy's back at the repair shop. They hooked up a GMC scanner to it the other day with no problem until my kid tried to drive it home. They're going to scan it again now that the SES light is on with the P0441 code. I don't know if the the GM scanner is going to give them any more information. The first mechanic I took it to suspected the valve (they replaced the hose so that should be okay).

drdd - I have no idea if it has CPI. We've only had the truck three weeks.

[taylorman]

I'm not 100 percent positive, but I thought 93,94,95 all had CPI injection. I know 93 does, I own one and have had to replace it. CPI injections are not known for being great injection systems, but they do work. They are easy to change but expensive. They are usually sold as a kit, but you can get the system by the piece if you know where to look. Anyhow, if that your problem should be a 10-20 minute fix once you get the part. Good luck.

[sail978]

Picked up the truck last night from the mechanic. He replaced one of the solenoids and hopefully that has done the trick. He's driven it about 40 miles so far with no problem. We're keeping our fingers crossed.