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JamesH, Technician
Category: Lexus
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Experience:  Auto Service Tech
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2001 lexus ls430: timing chain..000mi..serpentine belt..cracked

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I have 2001 lexus ls430 and was told need to have timing chain replaced at 90,000miles(a little late I have 218,000mi) does it really need done? also serpentine belt is cracked, & code po420&po430 catslyst system efficiency below threshhold bank 1&2? Do all 3 catalytic converters have to be replaced? Where can I get done reasonable? Live near Green Bay,WI but travel whole state for work. Help?
Yes, the timing should be serviced. If you wait too long when it does go you will have alot more issues. You could severly damage internal componants inside the engine. The belt is a inexpensive effortless task that should be performed right away as if not when it slips or breaks you will loose all function of the vehicle. The two codes are for the O2 sensors there are 4 of them and they should be replaced every 100k miles. I have attached pictures below. The best place to get it done is at a local auto repair shop. I would make some calls and find the best prices. Also sometimes local colleges will take on the jobs for a nice car like this at a very discounted price. You would have to contact the local colleges auto department for details. Let me know if there are any further questions.

Oxygen Sensor (Part 1)
Oxygen Sensor (Part 2)
Customer: replied 8 years ago.
So if those are the codes you think it's just sensors that need replaced not cat.converters? Is there a way to know for sure?
Thats correct. There are tests that can be done by an experience tech with the proper tools. I will send the steps they do at the shop. The O2 sensors are suppose to be replace regularly so I would think changing them would take care of the issue. Let me know if you have any other concerns. Thanks


DTC Detecting Condition

The ECM compares the waveform of the oxygen sensor located before the catalyst with the waveform of the oxygen sensor located after the catalyst to determine whether or not catalyst performance has deteriorated.

Air-fuel ratio feedback compensation keeps the waveform of the oxygen sensor before the catalyst repeatedly changing back and forth from rich to lean

If the catalyst is functioning normally, the waveform of the oxygen sensor after the catalyst switches back and forth between rich and lean much more slowly than the waveform of the oxygen sensor before the catalyst.

But when both waveform change at a similar rate, it indicates that catalyst performance has deteriorated.


  1. Connect the LEXUS hand-held tester to the DLC3, or connect the probe of the oscilloscope between terminals OXL1, OXL2, OXR1, OXR2 and E1 of the ECM connectors.
  2. Start the engine and warm it up with all the accessories switched OFF until engine coolant temperature is stable.
  3. Race the engine at 2,500 - 3,000 rpm for about 3 mm .
  4. After confirming that the waveform of the heated oxygen sensor (bank 1, 2 sensor 1 (OXL1, OXR1)), oscillate around 0.5 V during feedback to the ECM, check the waveform of the heated oxygen sensor (bank 1, 2 sensor 2 (OXL2, OXR2)).

If there is a malfunction in the system, the waveform of the heated oxygen sensor (bank 1, 2 sensor 2 (OXL2, 0XR2)) is almost the same as that of the heated oxygen sensor (bank 1, 2 sensor 1 (OXL1, OXR1)) on the left.
There are some cases where, even though a malfunction exists, the MIL may either light up or not light up.

Step 1

Steps 2 - 4


HINT: Read freeze frame data using LEXUS hand-held tester or OBD II scan tool. Because freeze frame records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.


These test are done by a specail scan tool, so if you can get it into the dealer they can tell you 100% for sure if its O2 or Cat
Customer: replied 8 years ago.
Do you know any local shops you'd suggest? About how much should timing chain, serp.belt and sensors cost to replace? Last question sorry, when I start car it says lexus link system is active(which I know no longer works lexus offered to replace it with sunglass holder) but then a man says an error has been detected call your lexus dealer, they say they've never heard that before?
I would get the sensors tested if its them order them from or another online parts store. Bring the parts with you and find a shop that will put them on or before you buy them to be sure.Some places wont onstall customer parts. But some do. You will safe the max The timing belt runs about less than 4 hours in the book to do so depending on there hourly rate and 50 for that belt roughly 250-300 the O2 sensors can get them from online retailers for 60-70 a piece take less than an hour per two so 220-260 for all three sensors installed. The link system you should have it removed if the dealer is doing this as it sounds like the programming is malfuntioning I have never heard this either I have checked the posts and found one thing so take this up with the dealer nearest you. I am not from your area but would have to say try calling local shops in the area tell them what you need and how much. Serp belt id like 30 if u get it yourself through dealer its 50 and the 50 to install. Like I said check in on the different shops. I would have to inform you to get the link system deactivated which the dealer can do this since its a trecall. Here is the information about the item. Thanks again.


September 11, 2003

'01 - '03 LS 430


Some customers with 2001 - 2003 model year LS 430 vehicles equipped with the Lexus Link system may encounter a condition which causes a DTC 6 code to be present in the Lexus Link system. Improvements to the Bus Buffer software have been implemented to remedy this condition on the LS 430.

Applicable Vehicles
^ 2001 - 2003 model year LS 430 vehicles.

Parts Information

Repair Procedure

Refer to TIS (Technical Information System): 2003 LS 430 Repair Manual, Body Procedure Mechanical, Luggage Compartment Door and Hinge, Removal.

Warranty Information

Applicable Warranty **

This repair is covered under the Lexus Comprehensive Warranty. This warranty is in effect for 48 months or 50,000 miles, whichever occurs first, from the vehicle's in-service date.

** Warranty application is limited to correction of a problem based upon a customer's specific complaint.


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