furballi

Update:

Swapped a known good throttle control motor. Still hear buzzing sound. Engine still go into limp mode when warm. Throttle body is clean. Plugs are good. Throttle posistion sensor tested OK per Toyota service manual...1200 to 3200 ohm.

Cleared ECU and went for a test drive to warm up the engine. Limp mode was activated 5 mile out. No feedback from the gas pedal, except for the last 5-10% when the throttle valve is controlled by the throttle cable attached to the Accelerator pedal position sensor (APPS). Measured the 5VDC input and ground wires of APPS. Both were OK. But the two output wires on the APPS were bouncing all over the place when I rotate the lever on the APPS, with reading as low as 0VDC with no pressure on the lever.

Took the car to Pey Boys for a free code check. Only P1120 was displayed...fault in AAPS.

The APPS tested fine at room temperature, including resistance test and input/output tests. But when the APPS heated up during driving, the wiper contact arms inside the APPS bounced against the variable resistor pads, causing the ECU to throw the engine into limp mode due to improper output signal.

I know some members may have a new APPS part number 22060-46010 sitting around during troubleshooting. I'm in S Cal and would like to purchase this item, cash. Best price online including shipping is $275. Please chime in if you know of a source with cheaper price.

TIA,
F

Rising2010

Hey guys I would love to hear your opinions on my issue with a 2007 Lexus IS250.

Around 3 months ago my rack and pinion failed. I had it repaired but the repair was not 100% as we could not find a particular bearing. Anyway the car was still drive-able with the repaired rack and pinion. I needed two new front tyres so I bought those and then did an alignment. While waiting for the alignment after moving my car and hearing a clunk after turning from the rack and pinion about 10 minutes later after the alignment we saw that the oil maint light was flashing and the trac on symbol i.e. the symbol of the car on a slippery road came on also a beeping sound comes every 10-15 seconds or so from the dashboard. The car bucks, the brakes are almost useless and the car creeps along so the car is definitely in limp mode.

I also think I need a new gas cap since when I turned it so see if it was closes correctly I heard a click but when it turn it again it clicks so something seems to have gone wring with the click mechanism.

Now for the final thing in my engine bay the mechanic who worked on the rack and pinion unfastened one of the vacuum hoses and I cannot put it together so I am wondering if that is also a contributing factor.

I am planning to take it to a mechanic (although with limp mode issue this is a headache) to see if he can fasten the cable. I am also going to fill the tank at a different gas station because the last time I filled the tank the click went off indicating that the gas tank was full but when I started the car the gauge showed it was only 3/4 full.

I was also thinking about buying a new gas cap cover as well. I bought the new bearings for the rack and pinion and its on its way.

Please let me your thoughts on my limp mode situation and my situation in general? Thanks in advance.

az-dave

Probably the Accelerator Pedal Sensor also called the "Lever Assembly".

furballi

I'm almost certain it's the APPS. Will repost later this week when I get the part.

furballi

I took apart the APPS yesterday and attempted a repair. It works! No more check engine light.

So it was indeed the APPS that went bad (open circuit) once the it warmed up from the engine heat.

@ AZ-DAVE or others who may have a full 1999 GS300 shop service manual:
Please PM me if you could provide me with a copy.

TIA,
F

az-dave

So you took the ring-sensor apart on the APPS and cleaned it or repaired it, or replaced it?

I have the service manual electronic somewhere...I honestly used it once and then found I went faster without referring to it...however the schematics may come in handy....then again at 262K miles, and already having replaced stuff like the entire tranny myself without a manual, im not sure I will use it.

I dont even know what computer or where its stored. hehe

furballi

I repaired the old defective APPS by machining a new add-on gizmo that would allow the APPS to not go open-circuit when warm. Toyota decides to hose us by charging $400 list for a part that would cost less than $30 to manufacture!

I'm looking for the full 1999 GS300 service manual. Someone posted a download link on this thread, but it was taken down by Toyota. I think I have a leaking front crankshaft oil seal. May need to remove the radiator and cooling fan to replace this item.

The ECU is stored in a rectangular black box on the driver's side, between the radiator and the left front headlight. It's next to the diagnostic terminal connector.

Thanks for your input.

burny

Man this limp mode crap is puzzling me. My daughter has a 2002 GS300. I replaced APPS about 2 months ago and issues didn't come back for about a month. Replaced fuel pump and filter 2 weeks ago and issues went away until she made a 90 mile trip down the interstate yesterday. Limp mode again. There has never been a code thrown, this is why it is so puzzling to me. Cleaned MAF really good last night and ran car today myself for about 20 minutes and never got the limp mode. Actually, I never have been able to get it. She and her boyfriend both have experienced it many times. They traveled 45 miles down interstate with hazard lights on yesterday.

Next thing I am going to do is the throttle control motor check. Can someone explain to me why no codes are being thrown? If it was the MAF that was dirty, then that might explain it. When I tap the MAF after car warms to op temp, it did change the idle very very slightly. Some say that is a sign of MAF going.

furballi

Disconnect the APPS harness and verify that each of the four wires are showing "continuity" going back to the ECU. You may have an intermittent short or open circuit. Wiggle the harness during testing. Repeat for the TPS and control motor harnesses to make sure that their wires are also good.

When the car goes into limp mode, make sure that there is 5VDC input at Vc, plus DC voltage outputs at VTA1 and VTA2 of the APPS. If VTA1 and VTA2 are bouncing around or go to zero even when there is 5VDC input, then you have a defective APPS. I would only suspect the control motor when you've confirmed proper operation of the APPS when warm.

burny

Thanks, will trouble shoot some more this weekend. Car is parked int he garage right now and seemed fine yesterday when I test drove it after cleaning MAF.

furballi

I would focus on the APPS, TPS, and control motor if there is no stored trouble code. Also perform the resistance tests per Toyota when you check for wire continuity.

MOTOR:
terminals 1 and 2 should be 0.3 to 100 ohms
terminals 3 and 4 should be 4.2 to 5.2 ohms

TPS:
terminals Vc and E2 should be 1200 to 3200 ohms

APPS:
terminals Vc and E2 should be 1200 to 3200 ohms

If engine goes into limp mode when warm, then check for incoming 5VDC and 0.6VDC to 5VDC output at VTA1 and VTA2 at the APPS and the TPS. The APPS is especially prone to failure that would result in erratic or no VTA1 and VTA2 output when warm.

Turn ON the ignition but do not crank the engine or step on the gas pedal. Connect an OBD II reader and confirm that the throttle position is 14.8%, plus minus 0.8%. Adjust by rotating the TPS as needed. You can also get pretty close to spec by measuring and adjusting the VTA1 terminal to 0.732VDC (second terminal from the top). You should hear a faint buzzing sound coming from the control motor. Now rotate the APPS lever by about 15 degree and release. The buzzing sound from the motor should be a little louder.

You may need to connect an ELM327 OBD II reader to a notebook and drive to obtain real time data of the absolute throttle position along with other incoming parameters to isolate the failure mode.

Trying stabbing at the gas pedals several times when you do the test drive. Problem usually surfaces when applying gas under warm/hot condition. Also remove the battery terminal for one hour to clear the ECU.

burny

great info, thanks. I really appreciate the time you took to offer this input.

furballi

NP! Post back with your results. Toyota designed a flawed APPS. I bought a new APPS, but decided to disassemble my old APPS to see if I can decipher the failure mode. Took me three hours to make the corrective mod. So far so good. I still have a new sealed APPS (P/N 22060-46010) available for sale. Paid $275 with Toyota invoice. Local cash pickup in S Cal only.

I can help members who are local to S Cal trouble-shoot a defective APPS. The APPS will almost always test OK when cold. This part will usually fail when the engine is warm, resulting in erratic or no signal output at the VTA1 and VTA2 terminals. List price at Toyota is $400, but you can buy it online for about $300.

http://www.toyotapart.com/22060-46010.html

burny

yeah, like I mentioned. I replaced the APPS a couple months ago and was sure that was the fix. I should have tested the resistance, but didn't. Lesson learned. It has got to be the throttle control motor. Friend is coming by tonight with a fancy scanner and will see what codes are embedded in that bad boy. It appears 20-30 minutes driving will not trigger the problem. it takes a little more than 30 minutes. I have yet to experience this infamous limp mode.

furballi

The ECU must display a check engine light before you can retrieve any stored trouble code. The checking procedures for the APPS and TPS are the same. If they work OK after 30 minutes of driving, then there's a good chance that the stepping motor with clutch assembly is bad. You can turn off the engine, wait 30 seconds, and restart the engine to see if there is control voltage present at the motor (terminals 1 and 2). If there is a change in control voltage but no throttle movement when you move the APPS lever, then the motor is bad. You can buy a replacement unit from Rock Auto or Autozone for less than $200.

A bad motor should trigger a check engine warning light with code P1128. Code P1120 or P1121 is usually associated with APPS.