tjsss

Hi Im Back, Thanks Morgan for your reply. Yes you were correct in your answer to replace the passenger side O2 sensor, but Lexus does not like Delphi O2 sensors. Despite a guarantee from the supplier of OEM equivalent the Delphi sensor did not work and caused considerable headaches as a result. So a word to those that seek an answer, do not use Delphi in place of Denso. They will not work despite being a third of the price. Well it was worth a try. Delphi sensor was 125.00 CDN vs 320.00 for Denso from Toyota/Lexus dealer supplied here in Toronto Canada. After much searching through this forum and other Lexus forum's I purchased 2 Denso aftermarket O2 sensors from www.densoproducts.you know the rest for 130.00 US + 30 shipping and GST 22.00 (SO LESS THAN 200 CDN. for the 2) They shipped via USPS with tracking so that I could watch the package take 2 days to get to Canada Customs and spend the next 7 getting cleared and delivered via Canada Post. So if you can wait I highly recommend this source for Denso replacement 02 sensors. If you are getting the P0125 code continually and the voltages are similar to the above, Bank 2 vs Bank 1, 2:1 ratio both of your pre-cat sensors need replacing. They must be replaced with 234-4169 part. If NOX values are low and/or in limit, the catyltic convertors should still be OK. Getting the right replacement O2 sensor is extremely important. Just thought I would update forum with results/resolution. I have to add having a patient understanding mechanic who also would rather replace only what needs to be replaced vs replacing item after item after item until issue is resolved is worth his weight in gold. I am glad I've got him!! Hope this helps someone else. TJSSS

Help Needed with diagnosis of emission failure and cont'd ODB code P0125, fail to closed loop. Hi There, I hoping to find someone who may have experienced the same type of problem or someone knowledgeable in the witchcraft of emissions interpetation/Lexus codes. I and a number of people I have consulted have come up empty with solutions apart from replacing the entire fuel system / emission system / catalytic system. 1998 gs 400 emission failed due to ASM2525 HC ppm limit 52/180 value, idle limit 150/230 value, CO% limit ASM2525 limit 0.29/4.30 value, idle CO% limit 0.70/4.01 value. NOx ppm passed. ODB codes history First set of codes were PO125 temp for closed loop, P0150 B2S1 circuit malfucntion, P0153 B2S1 circuit slow, P0171 system lean, P0150 B2S1, P0153 B2S1. Reset ECM, replaced B2S1 O2 sensor (original Denso with Delphi OEM 4 wire LTW.7595, 0938T1 coding on sensor), replaced cooling system thermostat WITH OEM. Emission failed again with codes again PO125 temp for closed loop, P0150 B2S1 circuit malfunction, P0153 B2S1 circuit slow ONLY. HC and O2 values consistent with first result. Reset ECM, road test until CEL and checked code, only one P0125. This is first emission fail for a routinely maintained GS 400. Mileage is high but was also on previous 2 year emission pass with flying colours. Your expert advise would be greatly appreciated as only other thoughts are CAT replacement/injectors etc which would be costly mistake to make. HELP!! Trim Values at idle Ignition advance - 11.0 deg Injector Pulse Width - 2.69 msec Long Term FT Bank 1 - 8.59% Long Term FT Bank 2 - 15.62% Mass Air Flow 4.7 g/s O2 Sensor 1/2 Volts - 0.61 V O2 Sensor 2/1 Volts - 0.00 V Short Term FT Bank 1 - -0.78% Short Term FT Bank 2 - 19.53% Total FT Bank 1 - 1.00 Total FT Bank 2 - 1.00 DTCS - 2 Ignition Advance 12.0 deg Long Term FT Bank 1 - 8.59% Long Term FT Bank 2 - 15.62% Mass Air Flow 4.4 g/s O2 Sensor 1/2 Volts - 0.50 Volts O2 Sensor 2/1 Volts - 0.00 Volts O2 Sensor 2/2 Volts - 0.87 Volts O2S B1S1 Lean/Rich 0.00 msec O2S B1S1 Lean/Rich 0.00 msec O2S B2S1 Lean/Rich 0.00 msec More info Engine Speed 736 RPM Coolant Temp 203 degF O2 Sensor 1/1 Volts 0.67 Volts Vehicle Speed Sensor 0 mph Calc Engine Load 14% DTCS 2 Ignition Advance 12.0 deg Long Term FT Bank 1 8.59% Long Term FT Bank 2 15.62% Mass Air Flow 4.2 g/s O2 Sensor 1/2 Volts - 0.19 Volts O2 Sensor 2/1 Volts - 0.00 Volts Please help! Apart from beginning the replacment of components without true justification that they are faulty, I intend to check wiring harnesses carefully and ECM. Thanks!!

1998 GS 400 Black on Tan with Lexus chrome 17" Bridgestone Potenza and winter black aluminum 17" Goodyear Alpine dedicated tires. Clock reads 316,689 kms here in Toronto Canada. Bought used at 280,000 km three years ago for 7,000. Best money I have ever spent. I will never own any other car than Lexus from now on. Car is perfect outside/inside and a pleasure to drive and own. Oil is changed every 5,000 km with synthetic and repairs have been limited to only normal wear items i.e. brake components, tires, wipers etc. What a well designed built car this is. Lots of power still at 300,000 + and whisper quiet inside and out. No rattles, ticking, or other age expected noises you would have with North American built at this point in a cars life. Speaks volumes. I will own this car so long as maintenance costs are limited to normal wear items. I expect another 10 years and double the current mileage would not be hard to realize. tjsss