smckellop Posted February 23, 2009 Report Share Posted February 23, 2009 I know there are a few other threads about this but I have not seen any for a 1999 Deville. I have a P0174 Error and I am wonder what are the first steps to take. Obviously I know that its a Fuel trim system lean bank 2 issue but I dont know what to look at first. Thank you in advance. Link to comment Share on other sites More sharing options...
BodybyFisher Posted February 23, 2009 Report Share Posted February 23, 2009 P0174 - Fuel Trim System Lean Bank 2 In closed loop operation, the PCM monitors the heated oxygen sensor signal voltage and adjusts fuel delivery based on signal voltage. A change made to fuel delivery will be indicated by the long and short fuel trim values which can be monitored with a scan tool (Tech 2). Note to self: I need to see if my Autotap can monitor long and short fuel trim values, It may be possible for us to monitor the long and short fuel trim values on our DIC with choosing the correct display. That needs to be researched. Ideal fuel trim values are around 0%. If the heated O2 sensor signal is indicating a lean condition, the PCM will will ADD fuel, resulting in a fuel trim value above 0%, the PCM will continue adding FUEL until the fuel trim value reaches 100% which is the maximum lean. If the maximum lean condition is detected, the PCM will set a DTC P0174. Pretty cool huh? Here is what the manual says to look at: Inspect the following items: Vacuum hoses for splits, kinks and proper connections Throttle body, intake and EGR valve for vacuum leaks (we recently had someone have a problem with the EGR tube that was corroded through) PCV valve for vacuum leaks, oil file cap or dip stick Contaminated fuel PCM and sensor grounds are clean and tight Air induction system AFTER MAF sensor for vacuum leaks Engine mechanical failure Check for exhaust leaks, missing or loose exhaust hardware Bank 2 O2 sensor installed securely and electrical connector not contacting the exhaust system or ignition wires Engine mechanical failure Vacuum leaks that ONLY affect bank 2 (intake manifold seals or cracked manifold, injector o-rings, etc) I find this code interesting because I also think that some of the symptoms above should also cause a P0300 misfire like the injector o-rings. How is the engine idling and accelerating? Do you have any other P codes? Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
smckellop Posted February 23, 2009 Author Report Share Posted February 23, 2009 I can not currently tell a difference in the way the car operates. I was considering resetting the engine light to see if it comes back on. I will check a few things tomorrow and see what happens. Link to comment Share on other sites More sharing options...
smckellop Posted February 23, 2009 Author Report Share Posted February 23, 2009 The light went out today before I had a chance to look at anything. I will wait and see if it comes on again and then check the items. Link to comment Share on other sites More sharing options...
PAUL T Posted February 24, 2009 Report Share Posted February 24, 2009 Does it have a hard cold start? I got that code when I had a hard cold start. Bodybyfisher gave you all the things to check. I would concentrate on a vacuum leak or plugged PCV. My problem was solved when I changed out the fuel pump relay with one of the others. You may try that. I even changed out the O2 sensor but it did not change anything. I would start with the air filter and make sure there are not any leaks in the air intake system. Link to comment Share on other sites More sharing options...
MAC Posted February 24, 2009 Report Share Posted February 24, 2009 When my exhaust manifold O2 sensor went bad, I believe I was getting the P013 code. Eventually, the sensor malfunctioned enough to cause the P094 code set. Since I replaced the O2 sensor, no more codes. P013 (E013) Right Oxygen Sensor Not Ready P046 (E046) Right to Left Bank Fueling Difference Link to comment Share on other sites More sharing options...
jeremyslar Posted March 10, 2011 Report Share Posted March 10, 2011 i'm having a similar problem. i have p0174 and p0171 fuel trim system lean on bank 1 and 2 Link to comment Share on other sites More sharing options...
joeb Posted March 10, 2011 Report Share Posted March 10, 2011 vacuum leak. maybe plenum? any rubber hose on intake. how about blow off valve. just noticed mine is starting to whistle. yes, i get p0174 occasionally. been a few weeks since code. Link to comment Share on other sites More sharing options...
Ranger Posted March 11, 2011 Report Share Posted March 11, 2011 i'm having a similar problem. i have p0174 and p0171 fuel trim system lean on bank 1 and 2 Being a 2000+ engine and having both codes I would almost guarantee you that your plenum is ripped. Link to comment Share on other sites More sharing options...
caddypete Posted March 11, 2011 Report Share Posted March 11, 2011 Bank 2 being the front bank, I would check your oil fill cap and dipstick are properly seated first. That would add unmetered air into that bank. With any luck it will be a simple stupid thing especially since you have no noticable engine irregularities Link to comment Share on other sites More sharing options...
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