jkosasih

did your mechanic check the EFI fuse, are they any spark/fire in the sparkplug? it could have a bad coil and the igniter, check the fuel pump relay or fuel pump itself.

To REMOVE ECT SENSOR located next to the radiator caps ( close to dog bone engine mounting) Disconnect the ECT sensor connector. Using a 19 mm deep socket wrench, remove the ECT sensor and gasket. INSPECT ECT SENSOR Using an ohmmeter, measure the resistance between the terminals. Resistance: at 80F degree it should read around 2K ohm if the resistance is not as specified, replace the ECT sensor. REINSTALL ECT SENSOR Install a new gasket to the ECT sensor. Using a 1 9 mm deep socket, install the ECT sensor. Torque: 20 N.m (200 kgf.cm, 14 ft.lb.) Connect the ECT sensor connector. REFILL WITH ENGINE COOLANT, it will be a good idea to change your thermostat as well.

First of all is your battery light (inside the instrumental light) come on? check your fuse make sure your alt fuse is not blown, then check the alternator it self. To check the alternator the easy way, first before you crank the engine you check the battery volt by using the voltmeter, read howmuch volt is the battery, if it is over 12 that is a good battery, if it is below the 12 then go to the next job. Start the car (jump if you have too, but after it start don't forget to take the cable jump off) while the engine still running re-check again the reading on voltmeter to your battery, if the alternator is good it should read between 13-14 volts if it still read the same before the car start than your alternator is not good.

You need to use an OBDII scanner in order to read what cause the check engine light on. It won't take more than 20 second to read it, if you don't have a scanner you need to borrow one or pay someone (small shop) just read it, then you go from there. If it is oxigen sensor there is 2 bank/sensor make sure which one, it could be also bad EGR valve and etz.......but still you need scanner to read the problems, don't guess it could cost you more money. It depend where you live Autozone has the OBDII scanner and they usually let you use it to see what is the problem.

do not guess without reading from the code. you need to read what code from scanner (OBDII) and go from there.

Check the ignition coil, there are two coils on your sc400.

Dear soarer479, I have answered your question before here is the link that you have asked just incase you forget. http://us.lexusownersclub.com/forums/index...howtopic=10177& ;)

If your EGR Valve is clogged with carbor, your car will not run smooth especially at idle. If your car still running smooth then is the modulator valve problem.The EGR modulator valve that I've known only can be found at dealer. Check with dealer about return policy, I am very sure is your EGR modulator valve is bad, if not then just return back to the dealer. It won't take that long to change it, if is not the modulator bring it back the same day. Don't forget to reset your computer after change the modulator valve.

Hi Matatan, Yes check engine light is off till now. First I check the EGR by using the vacumm and is working properly (the engine start stumble when you start vacumm) so the modulator that cause the check engine light problems, the valve quit working at 178K miles, now already 180K with no problem just the instrumental light just went out, but I already replaced it. Good Luck

go get replacement at pepboys is under $100, 02 sensor bank1 sensor1 locate under the hood just below the firewall. after you replace it you need to pull the EFI fuse next to the air filter to reset the ECM (Computer).

2 things, first your alternator could be bad, second is the battery itself. My bet will be on the alternator cause it should charge the battery, if it's not working right the light indicator will turn on on the instrumental panel.

Found the solution, the EGR modulator had a bad valve, replace it cost $76.00. The EGR Modulator is connected to the EGR Valve. Clear the code and now working great no more check engine light. So if anyone who has code PO401(EGR insufficient flow) test your EGR Valve first make sure is working and not cloged, then if it still on the check engine light the modulator will be the one that cause check engine light. ;)

Thanks skperformance, yes the vaccum works, everything works fine, I have no idea why the check engine light keep coming on, I have cleaned the egr valve, egr modulator, even the hose is good. I have this car with 178K miles, at 170K valve start to made some click noise, so I adjusted it by changing the right stem, now is smooth but at 8K miles later the check engine light came on and I check with the scanner, give me a code PO401(insufficent flow on EGR).

Hi Everybody, I have 96 ES300 with 178K miles, runs very well until lastweek the check engine light came on, however car drive and feel just like usual nothing seem to be a problem, so get it check and come up with code PO401 which is insufficient flow on EGR, took it a part clean it out really good, check the EGR using the pump test and the car begin to hesitate which is telling me that the EGR is good, I clean the EGR modulator and check all the hoses seem to be good condition, test drove no problem, however after you run about 30miles than stop about 10minutes then start the engine again and drive about 4 miles, the check engine light came on again. Once your reset the computer (pulling the EFI fuse) it will do the samething again and again. Could it be the EGR tempature sensor that causing this? Please help me out guys. Thank You in advance