Rich Sweitzer

I've found that Lexus uses a battery with the terminals "reversed" from the norm so be careful when buying a replacement (not as many options). I've used everything from Lexus labeled batterys (that didn't fit the battery box either) to Deka to the current Wal-Mart-labeled battery (requires a spacer to make it "tall" enough to fit properly). They've all had similar lifespans.

If it were my car I would want to know why the engine light came on before I reset the engine ECU. That's not normal after an oil change.

I Think that code 88 is actually the display segment test portion of the diagnostic routine.

I finally checked in my ’91 LS-400 repair manual . . . The early LS400 does indeed have something called Progressive Power Steering that varies the effort required to control the steering, depending on the vehicle’s speed. This is accomplished using an “electronically controlled hydraulic reaction chamber” on the rack. Engine vacuum is not used in any way to control the power steering system. The PPS system is somewhat sophisticated in that it has an ECU that monitors a speed sensor and in turn controls a solenoid valve that allows a varying degree of pump-pressurized fluid to bypass the rack assembly (the reaction chamber). If the steering suddenly became more difficult a low speeds I would check the connector and wiring to the solenoid valve on the drivers side of the rack. (You can check the continuity of the solenoid coil with an ohmmeter, it should be 6 to 11-ohms. If you do energize it directly from the battery (to listen for the “click”) only do so for a few seconds at a time as the thing can heat up and burn out. (The + terminal is on the right if you visualize from the connector end with the mounting tab down.) By the way, Lexus recommends a preliminary check of the system starting with tire air pressure, lubrication of suspension and steering linkage, front wheel alignment, steering system joint and suspension arm ball joint, bent steering column, security of all connectors in the system and the power steering pump pressure. Someone previously suggested using a cheap ATF to “flush” the system and then refill with Toyota type T-II fluid. I would personally be leery of using anything other than a Dexron compatible fluid in the system. Lexus specifies Dexron II in the power steering system at the same time they use T-II in the transmission. I would think that they would use the same fluid in both locations unless there was some compatibly issue. (Dexron and type T fluids have different friction characteristics.) Lexus also recommends bleeding the system after changing the fluid. A procedure in the manual describes the process [basically turning the steering wheel to one lock (left or right) and holding it there for 2-3 seconds, then to the opposite lock and holding it for 2-3 seconds, then checking the fluid level, adding more if necessary and repeating]. They also advise checking the fluid for foaming or emulsification, both signs that the system has air in it or that the fluid level is low. If you want to tackle more involved diagnosis of the problem post back with info request and I’ll provide additional data as needed.

I believe that Mikado Technology Company, 1435 Huntingdon Avenue, Suite C, South San Fracisco, CA 94080, +1 (650) 615-9966, mikadotechnology@yahoo.com are the folks that rebuild the AC ECU for around $300.00. Pace Compressor should be able to help you with the AC compreessor clutch. http://www.auto-air-compressor.com/contact.htm. They sell a rebuilt compressor, complete with clutch, for about $300. Good folks to deal with too. A new clutch from my local lexus dealer was just less than $300. First thing that I would do is check the wire going to the compressor clutch with a voltmeter (not the rotation sensor on the back of the compressor). Should have 12 volts on it to engage the clutch. Curious though, if the ECU is calling for the compressor to engage but it doesn't see the correct speed information coming back from the comrpressor's speed sensor it should assume a compressor lock-up and give you the green flashing AC light . . .

Correct, the valve is actually screwed into the power steering pump below the reservior, and it taps into the pressure side (as opposed to the return side) of the pump.

Which fuse panel do you think is at fault, the one just above the driver's left knee or the one just behind the battery ?. There aren't that many connections in the one behind the battery (although they are all rather high current). You might be able to "recondition" the connections in question with one of the Cramolin products ["grease", (with silicon particles)] from Caig Laboratories. They are excellent at cleaning and preventing corrosion in electrical connections.

A couple of long shots to look at . . . . When you changed the fluid did you purge the air from the system by turning the wheel lock-to-lock several times while the engine was running? (Probably shouldn't have required that given the fact it worked ok for a while after you made the change, but you never know.) Another possibility is a clogged filter screen in the bottom of the fluid reservoir restricting fluid flow in the system. Also, is the system making any kind of noise, either consistantly or when turning the wheel. That can provide a clue as to the problem.

When you changed the fluid what did you put in? Dexron II automatic transmission fluid, or better I hope, and not power steering fluid. Otherwise you may have damaged components in the system. I've used Red Line D4 ATF synthetic in my LS-400's power steering unit with very satisfactory results. The stuff doesn't even warm up enough to expand to the "Full - Hot" mark when in operation.

Correction: The power steering pump is right over the alternator, not the starter. As pointed out the starter is buried under the intake manifolds in the upper center rear of the engine (in the "V" of the engine).

I think that the "88" is just a display segment test. The first part of the test routine on the AC ECU tests the display and the lamps. The second part of the test displays error codes and the third part runs the fan and damper doors through their paces. As to the fans, there are three associated with the radiator and AC condenser. One fan sits between the radiator and the engine and is driven by the engine through the auxiliary drive belt. This fan is shrouded and is coupled to its drive source through a hydraulic clutch. The other two sit in front of the AC condenser just behind the grill (part of the hood). They are electric, can run at two different speeds and can be operated by either a temperature sensor at the bottom of the radiator on the drivers side or by a high pressure switch in the AC system located in the liquid line just after the condenser (behind the passenger side headlamp). You can test the basic operation of this fan pair by pulling the connector to the temperature sensor on the radiator and then turning on the ignition switch. Doing so should cause both fans to run. (These fans are operated by three relays located in a relay box underneath the drivers side headlamp.)

Anything that affects the car’s “drivability” can defeat the TRAC system as well as problems with the TRAC system itself. Reading the codes from the various computer systems in the car is relatively easy. All you have to do is short various pins together in one of the two diagnostic connectors and turn on the ignition. No special scanner required (at least not on my ’91 LS-400). I’ll try to post the various pin-outs a little later as I don’t have the manuals in front of me. My personal experience with this problem stemmed from a bad secondary throttle position sensor. Both the TRAC computer and the engine computer told me that. (Replacement and adjustment was easy.) One of the O2 sensors is a good bet too.

If you ever have a chassis dynamometer test run on the car (such as those required by some States' emmissions test programs) be sure that the system is off. Otherwise serious damage to the driveline could result. Otherwise it should be fine to leave it on all the time.

My '91 LS-400 has 296,000 miles on it! High mileage at 60,000 or 90,000 miles?! Whatcha talkin' 'bout?! B)

Oh, one other thought. I wouldn’t try to do a conversion to R134a using one of the aftermarket kits available at the local auto parts store. To do a conversion you first need to repair any leaks in the system, regardless of the refrigerant used. These kits don’t provide a means to detect a leak. These kits also include new oil, either PAG or Ester. Both are very hygroscopic (they absorb water) so they need to be installed very quickly and the system sealed immediately (with a new receiver/dryer). (Both these oil types are major skin irritants, you need PVC gloves to handle them, and don’t breathe the vapors either.) Then a vacuum has to “be pulled” on the system for about an hour. If this step isn’t followed the system will have both air and moisture in it. The air will cause the system to perform even more poorly that it would with proper installation and the moisture will react with the other chemicals in the system to form an acid that will lead to very premature system failure (compressor lock-up, condenser rupture, expansion valve failure). If there is enough moisture in the system it can even cause freeze up of the expansion valve or worse. If you want to learn more about R12 to R134a conversion Haynes has a good manual on the subject for under $20.