Code 55 lean monitor popped up again
07-23-2018, 01:27 PM
#1
Registered User
Thread Starter
Join Date: Feb 2011
Location: St.louis
Posts: 433
Code 55 lean monitor popped up again
What’s up guy’s. I know I haven’t visited in awhile but life is life.
Anyways a few weeks ago going to work and ses light came on under power I let off the gas and light goes out so I hit it again and sure enough light came on.
First thing checked codes and 55 came up.
Checked fuel psi 42 key on 40 started on the throttle 50 and then light came on
No missing or stutters always starts but stretching it out light comes on and feels forever to accelerate.
Sprayed starting fluid everywhere and no change and hoses look good.
No new mods or changes one day it was fine then 2 days later this happened.
My guesses are chip (NC) crapping out
Injectors are shot at wot
O2 sensors are dented to Hell from exhaust so low
Other than that I’m just speculating
Thanks
Art
Anyways a few weeks ago going to work and ses light came on under power I let off the gas and light goes out so I hit it again and sure enough light came on.
First thing checked codes and 55 came up.
Checked fuel psi 42 key on 40 started on the throttle 50 and then light came on
No missing or stutters always starts but stretching it out light comes on and feels forever to accelerate.
Sprayed starting fluid everywhere and no change and hoses look good.
No new mods or changes one day it was fine then 2 days later this happened.
My guesses are chip (NC) crapping out
Injectors are shot at wot
O2 sensors are dented to Hell from exhaust so low
Other than that I’m just speculating
Thanks
Art
07-23-2018, 06:50 PM
#3
Registered User
Thread Starter
Join Date: Feb 2011
Location: St.louis
Posts: 433
Re: Code 55 lean monitor popped up again
I was hoping I’d get a code in that area but unfortunately I’m not.
i changed my o2’s over to the 94- style years ago so probably time to change anyways.
although I’m not the type of person to throw parts at it but I’ll give it a shot.
btw I do have a data logging program from one of the members here years ago but that was on an old laptop and probably a lost cause to figure what it was
i changed my o2’s over to the 94- style years ago so probably time to change anyways.
although I’m not the type of person to throw parts at it but I’ll give it a shot.
btw I do have a data logging program from one of the members here years ago but that was on an old laptop and probably a lost cause to figure what it was
07-23-2018, 07:42 PM
#4
Administrator
Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,651
Re: Code 55 lean monitor popped up again
DTC 55 only sets in power enrichment (PE) mode = heavy acceleration. PE mode richens the A/F mixture for power and torque. The ECM looks for a “rich” reading from the O2 sensor(s). If it sees a lean reading for more than 8 seconds it sets the code.
If I read your fuel pressure data correctly, you have:
- 42 PSI prime before the engine starts
- 40 PSI at idle (is that with or without the vacuum compensation line connected to the fuel pressure regulator ?)
- pressure holds at 50 PSI at heavy acceleration (is that WOT up above 5,000 RPM.)
The GM spec for fuel pressure is 43.5 PSI at idle with vacuum line disconnected, with an acceptable range of 41-47 PSI. When you reattach the vacuum line, the pressure should drop proportional to intake manifold vacuum, about an 8 PSI drop below the “no vacuum” pressure. Seeing 50 PSI on heavy accel seems too high.... but that would be contrary to seeing a lean A/F ratio in PE mode. Something sounds screwy with the pressures.
Scan9495 by member GaryDoug will also scan the 93 ECM.
https://www.camaroz28.com/forums/com...95-lt1-874306/
A data log review of the O2 sensor readings in PE mode would be useful.
If I read your fuel pressure data correctly, you have:
- 42 PSI prime before the engine starts
- 40 PSI at idle (is that with or without the vacuum compensation line connected to the fuel pressure regulator ?)
- pressure holds at 50 PSI at heavy acceleration (is that WOT up above 5,000 RPM.)
The GM spec for fuel pressure is 43.5 PSI at idle with vacuum line disconnected, with an acceptable range of 41-47 PSI. When you reattach the vacuum line, the pressure should drop proportional to intake manifold vacuum, about an 8 PSI drop below the “no vacuum” pressure. Seeing 50 PSI on heavy accel seems too high.... but that would be contrary to seeing a lean A/F ratio in PE mode. Something sounds screwy with the pressures.
Scan9495 by member GaryDoug will also scan the 93 ECM.
https://www.camaroz28.com/forums/com...95-lt1-874306/
A data log review of the O2 sensor readings in PE mode would be useful.
07-23-2018, 08:01 PM
#5
Registered User
Thread Starter
Join Date: Feb 2011
Location: St.louis
Posts: 433
Re: Code 55 lean monitor popped up again
Yes 9495 was the one I had but like I said been so long and never used it more than 5x
plus lap been long replaced due to battery failure.
yes psi jumped to 47psi with vacuum line from regulator pulled off
1st 6k 2nd 6k 3rd 6k 4th at 5k 120mph light comes on I let out. Before 4th no light.
the only thing I omitted from this was my pcv valve was bad and blow by and lots of smoke was pouring out.
Thats all fixed now and no smoke.
could I have good psi but poor flow and get code55?
cause I haven’t changed fuel filter yetis
plus lap been long replaced due to battery failure.
yes psi jumped to 47psi with vacuum line from regulator pulled off
1st 6k 2nd 6k 3rd 6k 4th at 5k 120mph light comes on I let out. Before 4th no light.
the only thing I omitted from this was my pcv valve was bad and blow by and lots of smoke was pouring out.
Thats all fixed now and no smoke.
could I have good psi but poor flow and get code55?
cause I haven’t changed fuel filter yetis
07-24-2018, 09:02 PM
#6
Registered User
Thread Starter
Join Date: Feb 2011
Location: St.louis
Posts: 433
Re: Code 55 lean monitor popped up again
I’m gonna re download that 9495 program and see what’s going on but when it goes in pe mode I can only think of o2’s or chip is programmed too lean at wot?
since I good fuel pressure and it came out of nowhere and only change was it rained the day before has me stumped.
both heatedo2’s and chip were installed 3yrs ago
since I good fuel pressure and it came out of nowhere and only change was it rained the day before has me stumped.
both heatedo2’s and chip were installed 3yrs ago
07-25-2018, 09:12 AM
#7
Administrator
Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,651
Re: Code 55 lean monitor popped up again
Are the O2 sensor harness connectors water tight? A “leakage” short between the B pin and ground could reduce the sensor output voltage. Couldn't be a direct short, or that would cause the lean code (44 or 64) to set in closed loop, when it's not in PE mode.
09-02-2018, 10:47 PM
#10
Registered User
Thread Starter
Join Date: Feb 2011
Location: St.louis
Posts: 433
Re: Code 55 lean monitor popped up again
Hey no problem and always try cause you never know if someone else runs into the same issue “search function lol”
everything still fine and 250k miles this motor still lives lol. I’ll eventually rebuild it
oil pukes out smokes everywhere dipstick blew out oil cap blows off lol. She gots lots of blowbye lol
everything still fine and 250k miles this motor still lives lol. I’ll eventually rebuild it
oil pukes out smokes everywhere dipstick blew out oil cap blows off lol. She gots lots of blowbye lol
Thread
Thread Starter
Forum
Replies
Last Post