TLDR: car went into limp mode and threw TRC-OFF and CEL, Lexus dealer pulled codes 47, 21, 28. Replaced TPS with part #89452-22090 and codes and CEL are gone but TRC-OFF light remains on. Dealer is not entirely sure how to proceed stating TRC wasn't offered on US models and he has no diagnostic procedure.

Hi all, I bought a 16k mile 92 Celsior a few months ago and it has had a few quirks. Half way home from the importer (a drive of 2,200 miles) it made a felt-more-than-heard thunk, lost most of its power, and threw the CEL and TRC-OFF lights. I had it flat-bedded to a Lexus dealer in Kansas City and rented a car to get the rest of the way home. They said when they looked at it the following morning it showed no signs of malfunction. They did not charge me, nor did they attempt to pull codes. I had the car shipped the rest of the way and have been driving it regularly since it arrived in early July. I should also note that the speedo and tach intermittently fail to read. I was driving it to drop off a friend the other night and it did the same thing again: Limp, CEL, TRC-OFF. I limped it to my local Lexus dealer who pulled codes 47, 21, 28 and said I need a new TPS. I authorized the replacement. Today they called to say the car drives fine, has no CEL or stored codes, but the TRC-OFF light is still on. They also said there is a ticking/clicking coming from the TRC module on startup. They are unsure what to make of what they called the "secondary TPS" for the TRC system. Any advice or documentation on troubleshooting the TRC system would be appreciated. I am also aware that my ECU may need new caps and I plan to send it, along with the EMV display, to the Soarer Surgeon in NZ for refurbishing in the near future. I'm just trying to find out if the problem is actually in the TRC system or if my planned ECU repair is likely to take care of it. Thanks in advance for any advice.

 

That's very strange. Toyota did offer the Traction control in the USDM for the Ls, labeled instead as TRAC, with a light that says TRAC-OFF, instead of TRC and TRC-OFF.

The traction control system is kind of a "secondary TPS" for the car. Depending on how different wheels are slipping, among other variables, the car has a two flaps in the throttle body to regulate wheel spin. If I recall correctly, the outer flap is used for the Traction Control system, and the inner flap is controlled by the gas pedal via the throttle cable. Each flap has its own TPS sensor, which is used to determine the position.

Just for support, here's the LS 400 1UZ with TRAC:


Celsior with "TRC":


If the techs are diagnosing the car, they should probably be looking under the TRAC (Traction Control) system for LS 400. It's not guaranteed that the LS and Celsior system will be exactly the same, but I would imagine they are virtually identical. Also note if your production date is before or after the US 1993 model year, and if your car corresponds with a 1992 or 1993 LS 400. The diagnosis of the system may change slightly between these years.

As for the CEL and TRC-OFF/TRAC-OFF lights going off, I'm not sure how to solve this problem myself.. My car is does not have TRAC installed. Although, I would definitely like to know what the solution is, when its found. Hope this is helpful.

 

Dealer Replaced both TPS sensors, waived labor, I just paid for parts. Seems to have fixed it.

 

Spoke too soon. Problem came back this evening. I'm thinking the ECU definitely needs that rebuild.

 

I know for a fact that the tps ticks a few times on startup if it's not lined up correctly when installed