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95 Suburban code 44 and 54 troubles

Tiny
SELLERSJAMES
  • MEMBER
  • 1995 CHEVROLET SUBURBAN
I have a 95 k1500 5.7L with 360,000 miles or so. I have issues with a code or two I can't figure out. Here goes, I bought the truck with high highway mileage and it ran. I was told it was the original engine but the tranny had been changed once. The truck ran but had an erratic idle at stopped speeds. There was a TDC 44 showing as well. I know a decent bit about this stuff so I started with the O2 and IAC valve, replaced them. Problem remained. I then went to the TPS and still no luck. Next were fuel and air filters, fuel injectors, pressure regulator. Nothing seemed to fix this problem. EGR finally popped into my head so I sprayed some stuff sround it and sure enough the diaphragm was cracked. I capped the ports and plugged the vacuum line and the erratic idle was gone but the code was not. Still I have a Lean TDC 44. A couple days ago I repaired a broken exhaust manifold that I knew could be the problem but it was not. I rechecked my codes and also found a fuel pump signal TDC 54 along with 44. 54 is new on here that I know of. I don't know whyit came up because the description tells me that the pump wouldn't be running for 2 seconds atleast and the truck doesn't stall or cut off. I did find out the converter was emptied also. I am down to thinking my problem is with an internal intake gasket leak, ECM, or possibly the fuel pump, maybe even the new O2 sensor since the very rich conditions may ruined it. Please help with this problem. Thanks in advance
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Saturday, November 17th, 2007 AT 9:17 AM

10 Replies

Tiny
PEAR69
  • MECHANIC
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The 44 code is a low voltage from an oxygen sensor present for 50 seconds while in closed loop operation OR your o2 sensor or sensors are bad. Oxygen sensors cycle from low voltage to a higher voltage continuously when they are up to temperature. With 360000 miles? Well my friend I'm going out on a limb and I'm not going to suggest, I'm telling you, change all the oxygen sensors on your truck, I believe in 95 there may be two of them. One before and one after the cat. But there could be three depending on how your exaust system is set up. The 55 code is a voltage not present at fuel pump. Well, if the pump is running I would say that there may be a dirty ground to blame for this. There is a ground wire connected to the frame cross support just before or after the gas tank, it pokes out of the wire harness leading to the fuel pump. Sometimes it's hard to see but it's there somewhere. If this wire is corroded or making a bad connection it could cause this problem. Check it out and clean it up it can't hurt. But if your engine is running without cutting off I wouldn't worry about a 55 code. Sometimes the computer will throw codes just for the hell-of-it to get your addention I guess. Let me know how you make out. This site runs on small or large donations, please try to make one Thanks

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Wednesday, November 21st, 2007 AT 11:18 AM
Tiny
SELLERSJAMES
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I completely understand the codes that is brought up and I appreciate you verifying no doubt. I did want to say my truck has 360,000 miles yes. However this lean code has been on since I bought it. I have capped off the EGR port due to a cracked diaphragm on the valve therefore sealing one possible vacuum leak. I also changed the O2 sensor (it only has one), fuel injectors, fuel filter, fuel pressure regulator, Idle air control valve, air filter, and last but not least welded a crack exhaust manifold back together as to keep the scavenging effect down pulling the cold air in the exhaust. I still get this 44 code. I do have a gutted converter, so open exhaust but I am not sure if that is a problem or possibly an internal intake gasket leak. I did notice today that if my codes come up I can park the truck and let it idle the light goes out after a period of minutes so this tells me it is only running lean while under acceleration for the most part. The low fuel pump voltage I will check this weekend with the wire you mentioned. Thank you
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Thursday, November 22nd, 2007 AT 9:08 PM
Tiny
PEAR69
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Slow down-chill out-- happy holidays-- the code 44 is a low VOLTAGE code NOT a LEAN code. Remember--an oxygen sensor works like this--When the engine starts the o2s is in a closed loop (electrical loop) until it is brought up to temperature. Some o2s have a heating element built in to bring it up faster, some don't. When the temp. Is high enough (about 50 seconds or so later) the o2s starts to sense the oxygen in the exaust. It tells the computer" everything is good here" by sending electrical voltage pulses back to the ECM.-- Kinda like morse code; --- - - - ---  --- - - - --- lol If you can get a high impedance D/C voltage meter and back probe the o2s. See if the voltage fluctuates from a higher voltage to a lower voltage at a rapid pace. The key is --a rapid pace-- If it doesn't do this fluctuation the o2s is bad. The fact that the converter is gutted very well may cause a brand new o2 sensor to go bad in a matter of minutes. If your engine doesn't cut out or anything I wouldn't go nuts trying to find the 55 code. Remember the 44 code is low voltage and the 55 code is NO voltage. No voltage tells me that the pump shuts off. If your engine doesn't shut off then this code is almost not believable.
P.S. I know what it's like to crawl under your own truck--bust up your knuckles--while dirt is falling in your eyes--and your pisses off because the stinkin check engine light is on and you don't know why. If the engine runs fine get some black electrical tape, put it over the check engine light and runn'er till she blows
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Friday, November 23rd, 2007 AT 1:05 AM
Tiny
SELLERSJAMES
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I have checked somewhere for that 44 code and yes it did say low voltage but it also said lean for more than 50 secs. I am saying lean as in low voltage as rich would be higher than norm voltage. I believe it to be a lean condition because I have checked the alternator output for proper voltage and also changed the battery just to make extra sure. With the truck running and both A/C's on, lights blazing the alternator shows like 13 volts out and the same at the battery. Nothing on it shows 14.2 to 13.7 or so. I have done some research and heard that could cause my issue but doing the voltage test I figured that would rule it out and the battery was an added bonus. Is there something else I could be overlooking in this area? Like I mentioned with the voltage, I am familiar with the o2 and how it communicates with an ever changing rich lean signal so getting an obd machine to check the sensors signal will be my next area of looking. If there is something with the voltage I am not looking at or checking do tell, please. Thanks guys for the input and hope you all had a great Thanksgiving!
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Friday, November 23rd, 2007 AT 7:54 AM
Tiny
RASMATAZ
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An oxygen sensor will typically generate up to about 0.9 volts when the fuel mixture is rich and there is little unburned oxygen in the exhaust. When the mixture is lean, the sensor output voltage will drop down to about 0.2 volts or less. When the air/fuel mixture is balanced or at the equilibrium point of about 14.7 to 1, the sensor will read around.45 volts.
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Friday, November 23rd, 2007 AT 8:40 AM
Tiny
PEAR69
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Your o2 sensor generates its' own seperate voltage. The battery voltage will only effect the heater on the sensor ( if your sensor has a heater). Code 44 has nothing to do with the battery or alternator voltage. Rasmataz has the right voltages but remember they fluctuate at a rapid pace.
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Saturday, November 24th, 2007 AT 1:48 AM
Tiny
RASMATAZ
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It has an HO2 sensor located at B see below


https://www.2carpros.com/forum/automotive_pictures/12900_ho2_1.jpg



www.eautorepair.net
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Saturday, November 24th, 2007 AT 2:03 AM
Tiny
SELLERSJAMES
  • MEMBER
  • 5 POSTS
I am assuming HO2 means Heated as O2 is not. I am almost positive it was a three wire sensor. I called about it to get a replacement and they argued with me at the parts store saying it has more than one, one pre cat and one post cat. I tried to tell them it has ONE. They told me it had one three wire and one four wire sensor. If I recall correctly it was the three wire sensor. I will recheck my connections as well as look into checking the bad ground and get back. Thanks for the help so far and hope something turns that friggin light off :lol:
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Saturday, November 24th, 2007 AT 7:23 AM
Tiny
PEAR69
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Sorry if I mislead you earlier you are right, the 95's have one oxygen sensor. They are in fact three wire and they are heated. The color code is as follows Black=ground, pink or pink/white=ignition 12 volts, purple=the voltage output. The pink wire is the heater and the purple wire is the wire that talks to the computer. Test the purple wire for rapid fluctuating voltages from.2v to.9v. These color codes come from the chassy wiring and not nessesarily the wire on the sensor.
I really think the gutting of the converter has a lot to do with the light. There is always black electrical tape, ya know, over the light. Lol
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Saturday, November 24th, 2007 AT 2:50 PM
Tiny
SELLERSJAMES
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I have replaced the converter with a new unit and with no luck. I have not changed the O2 sensor yet as I was hoping the one that is in it, recently purchased, was not shot. I still yet to check the voltage and see what comes of that.
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Sunday, February 3rd, 2008 AT 10:53 AM

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