check engine code help!!!
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check engine code help!!!
It has been a while since I have posted anything but I really need some help! I have a 1994 F-150 with a 5.0, automatic, and 197,500 miles on the clock. I have four codes appearing when I scan it.
I am getting a memory code for:
code 172, HO2S system lean (bank 1);
code 173, HO2S system rich (bank 1);
EGR flow insufficient code 332;
and an EVP sensor closed valve, above max voltage, code 334.
I am a bit confused at how I can get a code for both rich and lean at the same time on one O2 sensor. I am experiencing major power loss when driving and then all power returns as if a lightswitch was turned on. I replaced the EGR valve because it was bad, but I am having problems still with no power and terrible fuel mileage. Someone please help!!!!
I am getting a memory code for:
code 172, HO2S system lean (bank 1);
code 173, HO2S system rich (bank 1);
EGR flow insufficient code 332;
and an EVP sensor closed valve, above max voltage, code 334.
I am a bit confused at how I can get a code for both rich and lean at the same time on one O2 sensor. I am experiencing major power loss when driving and then all power returns as if a lightswitch was turned on. I replaced the EGR valve because it was bad, but I am having problems still with no power and terrible fuel mileage. Someone please help!!!!
Elder User
Joined: Feb 2007
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From: Mulege south Baja ca. Mx.
that probably means the the o2 sensor is working OK but is getting high and low readings. I would look for a probalm with the EGR and fix that and then reset the codes. your O2 problems will most likely go away.
the 334 code you will need to check out also. check both of your gas capes.
the 334 code you will need to check out also. check both of your gas capes.
Lead Driver
Joined: Nov 2002
Posts: 9,555
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From: Concord, NC
Those O2 sensor codes can also mean that the sensor is not switching, either due to a permanently rich or lean mixture or due to a failing O2 sensor. If it is due to the mixture being rich or lean, you will first have to find out what is causing the rich or lean mixture (fuel pressure regulator can leak, causing a rich mixture, for example) and fix that problem, otherwise, a new O2 sensor will just throw the same codes again. If you haven't already, I would reset the codes and go for a short drive to see which one comes back first, then start investigating. I think it is a little premature to condemn the computer itself just yet, but it certainly could cause some problems. I've seen a couple computers throw O2 sensor codes when they have failed internally, but those have all been OBD-II computers in 96 trucks.
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Well I have replaced the EGR valve already. I drove to class this morning and I had a hard time taking off and getting to 20 mph. I had the pedal to the floor and then I heard the truck backfire twice and it picked back up to speed. Well, atleast I think it was backfiring.. The gas cap problem I was told was specific to OBD-II computers. I had my doubts with the O2 sensor as causing the problems, I pulled it out and it looked fine and it looks to be recently installed but I know that just by visual inspection can not determine if it is bad. Could a plugged cat cause any of this? Is it a little weird that I don't experience most of these problems when I switch between tanks?
Fleet Owner
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From: Easton,Ks
A fuel system can cause these problems. Check the fuel pressure from each tank.
Hook a pressure gauge to the fuel manifold, ground pin#6 (circuit #926, LB/O wire) of the test connector and turn on the key.
Turn off the key switch tanks and turn the key back on.
You should get about 45 psi.
The Test connector:
http://i54.photobucket.com/albums/g91/subford/Fuel/DLC92-95.gif
Hook a pressure gauge to the fuel manifold, ground pin#6 (circuit #926, LB/O wire) of the test connector and turn on the key.
Turn off the key switch tanks and turn the key back on.
You should get about 45 psi.
The Test connector:
http://i54.photobucket.com/albums/g91/subford/Fuel/DLC92-95.gif
Last edited by subford; Apr 9, 2007 at 11:45 AM.
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Well I checked the fuel pressure with the key on and while running and I got 32psi on the back tank and 30psi on the front tank. I didn't ground out pin #6. Would this make a difference if I grounded it or not? I also noticed what sounded like a weird vacuum leak/spring coming from the fuel pressure regulator once I shut off the engine. I also changed the fuel filter and it seems to idle a little better too. Then I went to check the fuel pressure again but then my brand new fuel pressure gage started leaking from the dial. So I have to get a new one to check it again and post it here.
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Elder User
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From: Mulege south Baja ca. Mx.
if it started leaking it may have not been giving you good readings. get a good one and check it
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Fleet Owner
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From: Easton,Ks
Originally Posted by cougar_1987
Well I checked the fuel pressure with the key on and while running and I got 32psi on the back tank and 30psi on the front tank. I didn't ground out pin #6. Would this make a difference if I grounded it or not? I also noticed what sounded like a weird vacuum leak/spring coming from the fuel pressure regulator once I shut off the engine. I also changed the fuel filter and it seems to idle a little better too. Then I went to check the fuel pressure again but then my brand new fuel pressure gage started leaking from the dial. So I have to get a new one to check it again and post it here.
Doing this with the engine running can cause a fire.
With the engine running the fuel pressure will range from about 32 psi at idle if you have good vacuum to about 43 psi WOT.
Also you can pull the vacuum hose to see if fuel comes out of the nipple of the fuel pressure regulator and if it does the regulator is bad. The fuel pressure will also be about 45 psi with hose off if it is running.
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Well I finally got a second new pressuer guage and I got around 30-32 psi with pin #6 grounded. Then I tried it again and I got 40. Both times it held pressure. I started the engine and it ran at 32 psi but then I gave it gas, and held it, it jumped up to 39 and then dropped back to 32 psi. I then unhooked to hose to the reg and I got the same pressure readings as before but no gasoline came out of the reg. The vacuum hose does not leak going to the reg. When I shut the engine off with the vacuum hose disconnected I still heard this funny noise coming from the reg. When I switch between tanks the needle only drops 1-2 psi. Does this sound like the regulator is bad then?
Fleet Owner
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From: Easton,Ks
I would go for the regulator as it would be rare for both fuel pumps to putout low pressure.
The fuel pumps should be able to pump all the way up to 95 psi with a bad regulator stuck closed, of course this would blow the check valve in the other non-running tank.
I am going under the assumption that the regulator is stuck open.
The fuel pumps should be able to pump all the way up to 95 psi with a bad regulator stuck closed, of course this would blow the check valve in the other non-running tank.
I am going under the assumption that the regulator is stuck open.
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Junior User
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That is what I am leaning towards also. I highly doubt that both fuel pumps would go bad at the same time. When I was under the truck changing the fuel filter on Tuesday I looked at the front tank and it looks like a new tank. No rust on it, new lines from the fuel filter up to the engine. But that doesn't always mean there is a new pump in the tank too.
Senior User
Joined: Dec 2002
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From: Greenville PA
Wow, hey bud read my post, its very interesting, hope the regulator fixes your problem, I'm still trying to fix mine, I have replaced about everything, and checked and changed everything, I got a EGR code again, and have found that my Differential Return Sensor that feeds air to the EGR is not working, so I'm about to go out to the truck and pray that is the problem. Good luck.
Fleet Owner
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From: Easton,Ks
Originally Posted by Red Raider 4x4
I got a EGR code again, and have found that my Differential Return Sensor that feeds air to the EGR is not working
Here are two diagrams of the Differential EGR System.
Senior User
Joined: Jan 2005
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From: Chesapeake, va
Sounds like a plugged cat
You may be right on one of your first post. I have seen a plugged cat cause all kinds of problems with the EGR and the #1 condition is the truck won't go when you try to accelerate. Unscrew the O2 sensor and hook up a pressure gauge in the O2 hole (some vacuum gauges have a pressure side) You should not get more that 3-5 psi at any RPM. The bottom line is that it shouldn't build pressure prior to the cat.