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[rehr0001]

Hi all. I'm looking for a little bit of expertise here.

96LS400 128k

I've had my CEL on for about a year now w/ a bad 02 sensor. I haven't gotten around to changing it and my gas mileage and driveability has been great.

Earlier this week while I was driving to work I had a sudden buck as I let off the accelerator going about 45MPH coupled w/ my TRAC OFF light starting to flash. The bucking continued at certain speeds and I lost all acceleration. After I spent the day at work, I got back in the car to go home and it wouldn't start (low idle, then die). Eventaully I got it to start and had the same problems I mentioned above - no acceleration, bucking at certain speeds and noticed I went through 1/4 tank of gas in a 40 mile commute.

I went to autozone and got the codes - P0100, P0101, P0135, P0141, P0155, P0161, and P0403

From my understanding these are MAF codes, 2 O2 sensor codes, and an EGR code.

I ordered a remanufactured MAF and installed it tonight and there is no difference. From searching the forum, it looks like it may be the ECU.

I'm looking for some advice here ..... what would you do in the situation? Could just having completely bad 02 sensors cause this behavior? Is there something else I should be looking at?

My plan right now is to take it to the Lexus dealership to have them troubleshoot, but my concern I give them $100 for them to tell me to replace the ECU. How good are the dealers at troubleshooting this kind of stuff?

Thanks in advance,

Dan

[billydpowell]

Hi all. I'm looking for a little bit of expertise here.

96LS400 128k

I've had my CEL on for about a year now w/ a bad 02 sensor. I haven't gotten around to changing it and my gas mileage and driveability has been great.

Earlier this week while I was driving to work I had a sudden buck as I let off the accelerator going about 45MPH coupled w/ my TRAC OFF light starting to flash. The bucking continued at certain speeds and I lost all acceleration. After I spent the day at work, I got back in the car to go home and it wouldn't start (low idle, then die). Eventaully I got it to start and had the same problems I mentioned above - no acceleration, bucking at certain speeds and noticed I went through 1/4 tank of gas in a 40 mile commute.

I went to autozone and got the codes - P0100, P0101, P0135, P0141, P0155, P0161, and P0403

From my understanding these are MAF codes, 2 O2 sensor codes, and an EGR code.

I ordered a remanufactured MAF and installed it tonight and there is no difference. From searching the forum, it looks like it may be the ECU.

I'm looking for some advice here ..... what would you do in the situation? Could just having completely bad 02 sensors cause this behavior? Is there something else I should be looking at?

My plan right now is to take it to the Lexus dealership to have them troubleshoot, but my concern I give them $100 for them to tell me to replace the ECU. How good are the dealers at troubleshooting this kind of stuff?

Thanks in advance,

Dan

Are you sure you cat converter is not stopped up?? giving you too much back pressure?

[RDM]

Hi all. I'm looking for a little bit of expertise here.

96LS400 128k

I've had my CEL on for about a year now w/ a bad 02 sensor. I haven't gotten around to changing it and my gas mileage and driveability has been great.

Earlier this week while I was driving to work I had a sudden buck as I let off the accelerator going about 45MPH coupled w/ my TRAC OFF light starting to flash. The bucking continued at certain speeds and I lost all acceleration. After I spent the day at work, I got back in the car to go home and it wouldn't start (low idle, then die). Eventaully I got it to start and had the same problems I mentioned above - no acceleration, bucking at certain speeds and noticed I went through 1/4 tank of gas in a 40 mile commute.

I went to autozone and got the codes - P0100, P0101, P0135, P0141, P0155, P0161, and P0403

From my understanding these are MAF codes, 2 O2 sensor codes, and an EGR code.

I ordered a remanufactured MAF and installed it tonight and there is no difference. From searching the forum, it looks like it may be the ECU.

I'm looking for some advice here ..... what would you do in the situation? Could just having completely bad 02 sensors cause this behavior? Is there something else I should be looking at?

My plan right now is to take it to the Lexus dealership to have them troubleshoot, but my concern I give them $100 for them to tell me to replace the ECU. How good are the dealers at troubleshooting this kind of stuff?

Thanks in advance,

Dan

The worst thing you can do is just start replacing random parts. A MAF code rarely ever means the MAF is bad, it could be as simple as a bad coolant temp sensor tricking the ECU into seeing an A/F ratio fault, as the car will stay in the cold fuel map, thereby showing trouble with both the MAF, O2s, and the ignition primary circuit.

A proper diagnosis will not only show the codes, but how those codes relate to each other. Begin by narrowing down what parts can be faulty to trigger all the codes instead of just replacing all the parts.

The dealer will have a better scan tool than any OTC parts store and be able to monitor and access each individual sensor, so if you're questionable at diagnosing it yourself it's an easy way to know for sure. Even being the mechanic I am I sometimes send the car to the dealer to verify so I'm not guessing, I just had an ES300 yesterday that came up with three codes that were all possible culprits, it's easier and usually less costly to narrow it down to a specific item than to just replace all the parts on a whim.

[rehr0001]

Thanks, all for your replies.

Update:

I brought it in to Lexus. I guess one o2 sensor is completely corroded and hanging off of the vehicle, the other is badly corroded but still in place. They tell me they want to replace the MAF and both o2 sensors. i am waiting to speak to the mechanic, but I figured i'd pose the question here first.

Since I already replaced the MAF and didn't have resolution of the symptoms:

Is it possible the bad o2 sensors could cause the MAF codes on their own?

I'm thinking I'm going to replace the o2 sensors and see what happens.

Hi all. I'm looking for a little bit of expertise here.

96LS400 128k

I've had my CEL on for about a year now w/ a bad 02 sensor. I haven't gotten around to changing it and my gas mileage and driveability has been great.

Earlier this week while I was driving to work I had a sudden buck as I let off the accelerator going about 45MPH coupled w/ my TRAC OFF light starting to flash. The bucking continued at certain speeds and I lost all acceleration. After I spent the day at work, I got back in the car to go home and it wouldn't start (low idle, then die). Eventaully I got it to start and had the same problems I mentioned above - no acceleration, bucking at certain speeds and noticed I went through 1/4 tank of gas in a 40 mile commute.

I went to autozone and got the codes - P0100, P0101, P0135, P0141, P0155, P0161, and P0403

From my understanding these are MAF codes, 2 O2 sensor codes, and an EGR code.

I ordered a remanufactured MAF and installed it tonight and there is no difference. From searching the forum, it looks like it may be the ECU.

I'm looking for some advice here ..... what would you do in the situation? Could just having completely bad 02 sensors cause this behavior? Is there something else I should be looking at?

My plan right now is to take it to the Lexus dealership to have them troubleshoot, but my concern I give them $100 for them to tell me to replace the ECU. How good are the dealers at troubleshooting this kind of stuff?

Thanks in advance,

Dan

The worst thing you can do is just start replacing random parts. A MAF code rarely ever means the MAF is bad, it could be as simple as a bad coolant temp sensor tricking the ECU into seeing an A/F ratio fault, as the car will stay in the cold fuel map, thereby showing trouble with both the MAF, O2s, and the ignition primary circuit.

A proper diagnosis will not only show the codes, but how those codes relate to each other. Begin by narrowing down what parts can be faulty to trigger all the codes instead of just replacing all the parts.

The dealer will have a better scan tool than any OTC parts store and be able to monitor and access each individual sensor, so if you're questionable at diagnosing it yourself it's an easy way to know for sure. Even being the mechanic I am I sometimes send the car to the dealer to verify so I'm not guessing, I just had an ES300 yesterday that came up with three codes that were all possible culprits, it's easier and usually less costly to narrow it down to a specific item than to just replace all the parts on a whim.

[RDM]

Yes, as I said above the MAF code is just related to other symptoms. Since the O2s are giving incorrect readings the ECU is being tricked into thinking the MAF is bad too. Do not replace it until they've proven it is indeed bad, and this will only be possible when the O2s are replaced, the codes are cleared, the monitors are reset, and the car has been driven for several miles.

[rehr0001]

Yes, as I said above the MAF code is just related to other symptoms. Since the O2s are giving incorrect readings the ECU is being tricked into thinking the MAF is bad too. Do not replace it until they've proven it is indeed bad, and this will only be possible when the O2s are replaced, the codes are cleared, the monitors are reset, and the car has been driven for several miles.

Well, Lexus really didn't help at all. They wanted me to replace both of the o2 sensors and the MAF sensor. Told me that was all that it could be.

I said no way to the $2k and brought the car to a friend of a friend who is a mechanic and works for cash on the side. After about 10 minutes looking at my car he checked a fuse. That was the problem. I guess the fuse that blew sends power to the MAF, IACV, and the heaters for the 02 sensors. My 02 sensor that had corroded off and was dragging on the ground likely caused a short and blew the fuse. $.60 later, my car runs like a million bucks again (I replaced both of the o2 sensors too)

Thanks for your help and suggestions.

[lexfourcam]

I've been having similar problems with my ls. where exactly is the fuse located under the hood or under the dash?

[rehr0001]

It was the EFI #2 fuse - location 28 under the hood - 10 amp

I've been having similar problems with my ls. where exactly is the fuse located under the hood or under the dash?

[lexfourcam]

Thanks alot i'm gonna check this right now before i order a new maf and try to rewire the harness as well.

[Segun]

Thanks very one my 1996 lexus is fixed. It a 10 Am fuse. I change everything on the car mass flow. Wire. Cab spark plus and ecu and car still doing same thing until i read this post and know it 10 am fuse efi thank you

[Mikec55555]

Dude thanks so much