bain Posted April 23, 2004 Share Posted April 23, 2004 Engine Code 25, Air-Fuel Ratio Lean Malfunction. Any speculation on the probable cause of this and/or how to repair? Quote Link to comment Share on other sites More sharing options...
AWJ Posted April 23, 2004 Share Posted April 23, 2004 How well does the car run? I'll check the diagnostics when I get home. You're lean. Means not enough fuel. Could be anything in that area. I'll check the code. Quote Link to comment Share on other sites More sharing options...
AWJ Posted April 26, 2004 Share Posted April 26, 2004 (1). Main heated oxygen sensor voltage is .45v or less (lean) for 90 sec. under conditions (a) and (b ). (2 trip detection logic)* (a) Engine coolant temp. 60 C (140 F) or more. (b ) Engine speed : 1,500 rpm or more Trouble area: Open or short in main heated oxygen sensor circuit Main heated oxygen sensor failure Ignition system Engine coolant temp. sensor (2). Main heat oxygen sensor voltage is alternating above and below .45v at 5 times / sec. or more under conditions (a) and (B). (2 trip detection logic)* (a) engine speed: Idling (b ) engine coolant temp : Between 60 C and 95 C (140F to 203F) Trouble area: Open or short in injector circuit Fuel line pressure (injector blockage) Volume air flow meter (air intake) Engine ground bolt loose Foreign object in valve (3) Difference of air fuel ratio feedback compensation value between right and left banks is more than 10% for 30 sec or more under conditions (a) and (B). (2 trip detection logic)* (a) Engine speed : 2,000 rpm or more (b ) Engine coolant temp : between 60 and 95 C Trouble area: Fuel line pressure (injector leak, blockage) Mechanical system malfunction (skipping teeth on timing belt) Ignition system So there you have it. One or all of these issues - pretty much all related. When was your last tune up? Get a full tune up if you have not before. Change the timing belt if it has not been done. Replace all o^2 sensors and go from there. The factory service manuals are worth their weight in gold. Quote Link to comment Share on other sites More sharing options...
bain Posted April 26, 2004 Author Share Posted April 26, 2004 Car runs well, no other noticable symptoms. It does sit quite a lot now as Sandra drives her Miata on the cool sunny days. It was borderline on its last emissions test (I forget which test). Thanks for the invaluable advice!! Quote Link to comment Share on other sites More sharing options...
UCF3 Posted August 14, 2004 Share Posted August 14, 2004 david_meusa Writes: "Hi, 92 LS400, same problem. Did you fix that problem?" Dave: I would image. Are you experiencing the same problem? Quote Link to comment Share on other sites More sharing options...
david_meusa Posted August 16, 2004 Share Posted August 16, 2004 david_meusa Writes:"Hi, 92 LS400, same problem. Did you fix that problem?" Dave: I would image. Are you experiencing the same problem? Can't find big difference, 155K miles on it. I reset the code, after abt 15 miles, check engine light comes again. Looks like it is heat related? I used some fuel cleaner today to see what happen. Quote Link to comment Share on other sites More sharing options...
TMaxxTim Posted August 16, 2004 Share Posted August 16, 2004 I have a feeling it might be 02 sensor related, when's the last time, if ever, you've replaced them? Quote Link to comment Share on other sites More sharing options...
Ben2007 Posted June 24, 2007 Share Posted June 24, 2007 Engine Code 25, Air-Fuel Ratio Lean Malfunction.Any speculation on the probable cause of this and/or how to repair? I have a 91' LS400, recently I also got DTC 25 error code. My smog check failed with NO too high. Have you solved your problem ? What's the solution ? By the way, here are my smog check numbers: 15 MPH: CO2 14.7%, O2 0.3%, HC 10ppm, CO 0.00%, NO 1119 ppm 25 MPH: CO2 14.8%, O2 0.1%, HC 7ppm, CO 0.00%, NO 769 ppm Thanks Quote Link to comment Share on other sites More sharing options...
termin8or Posted July 15, 2007 Share Posted July 15, 2007 Same problem here. I checked the main Ox sensors and the heating elements seem to be OK. I have changed plugs and fuel filter, no luck yet. I plan on wires and caps & rotors next. (Ifigure bit probably needs it anyway. Then, I guess I will pull the injectors for cleaning. Tried injector cleaner w/o sucess. Quote Link to comment Share on other sites More sharing options...
whitesnake SC400 Posted April 14, 2009 Share Posted April 14, 2009 Has anyone of you solved the issue? I have same symptoms. After erasing engine error codes it (code 25) reappers after driving of highway for several minutes. Quote Link to comment Share on other sites More sharing options...
Aljsr Posted March 23, 2011 Share Posted March 23, 2011 In my situation, it was the fuel pump Quote Link to comment Share on other sites More sharing options...
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