codes 47 , 24

[jschunke]

my 1993  ls400 is in the shop for codes 47 (TPS) and 24 (air temp sensor).

After spending $800 on a new TPS and MAF the light still goes on,

I believe he changed the same parts twice to no avail.

I really don't want to lose this car. please help!

[Exhaustgases]

A code doesn't always mean that is the problem. And one bad thing about our OBD1 systems is we don't get all the information that an OBD2 system will report, so it makes it much more difficult to pin point the problem. These cars have the famous ECU leaky capacitor problems and that alone can cause many false codes or running problems.

Also there are other little things that can be or add to the problem like leaky vacuum hoses, the bearings in the idle air control motor. Also things like low voltage from bad connections due to corrosion with in connectors or wire junction points. A true auto tech would be trying to check for the signals from those items before replacing them. And first suspect the wiring and connections from them to the ECU. So if the parts are known good that were replaced then the problem is either getting the information to the ECU or the ECU itself.  The most important thing in this whole endeavor is to have the proper service information. You can go to the Toyota TIS site and get all the service manual info and even service bulletins that may cover the exact problem you are having. It is the best bang for the buck for the service information. I think its $15 for 2 days, of use.

[jschunke]

8 hours ago, Exhaustgases said:

A code doesn't always mean that is the problem. And one bad thing about our OBD1 systems is we don't get all the information that an OBD2 system will report, so it makes it much more difficult to pin point the problem. These cars have the famous ECU leaky capacitor problems and that alone can cause many false codes or running problems.

Also there are other little things that can be or add to the problem like leaky vacuum hoses, the bearings in the idle air control motor. Also things like low voltage from bad connections due to corrosion with in connectors or wire junction points. A true auto tech would be trying to check for the signals from those items before replacing them. And first suspect the wiring and connections from them to the ECU. So if the parts are known good that were replaced then the problem is either getting the information to the ECU or the ECU itself.  The most important thing in this whole endeavor is to have the proper service information. You can go to the Toyota TIS site and get all the service manual info and even service bulletins that may cover the exact problem you are having. It is the best bang for the buck for the service information. I think its $15 for 2 days, of use.

 

[jschunke]

thank you.

the mechanic said the ls400 is now only throwing code 47 (sub-tps).

after replacing it the second time and calibration he drove the car for two days without incident.

As soon as I drove it the engine light and traction light came back on.

[LSPaul]

I went through same thing (chasing down DTC 47) earlier in the year, after replacing and re-adjusting the sub-TPS on my '94. 

My experience with chasing down the sub-TPS issue is that the ultimate cure was to re-cap (replace the electrolytic capacitors) in the engine ECU, located under the glovebox, behind the lower dashboard kick panel. Fairly common with this vintage of Toyota/Lexus ECUs. The kits of new electrolytic caps sold on an online auction site (correct values, manufacturer, temp ratings, etc--$12-ish), will resolve it, once installed. You will need skill with electronics/soldering to do this job. 

Otherwise, watch for a used '93 or '94 (only) engine ECU and takes your chances.  If a used one works, go ahead and re-cap your existing ECU, as you'll eventually need it!

Paul