[NMuzj100]

A Readers Digest on the TPS/APPS issues with links to the relevant threads. Send me any feedback/corrections/recommendations in a PM and I'll make changes.

TPS = Throttle Position Sensor
APPS = Accelerator Pedal Position Sensor
TB = Throttle body

Known issue 1998-1999
Sudden lack of accelerator response, “Limp Mode” (e.i. approximately 25% power), power available only when "floored"
May be associated with cold weather
CEL with codes

• P0120 – TPS (98 FSM DI-38)
• P0121 – TPS (98 FSM DI-44)
• P1120 – APPS (98 FSM DI-104)
• P1121 – APPS (98 FSM DI-104)

In TRAC equipped vehicles may set "VSC/TRAC" and "VSC OFF" lights as well.
If engine is shut off the truck may start with no sign of the problem and drive normally.
If the truck drives without problem the CEL may go out after a number of miles.
Pulling the EFI fuse from the fuse block for a few minutes will reset the CEL.

Repeated occurrences are usually solved by the replacement of the APPS (~$270) and sometimes the TPS. (~$70). Dealers often recommend replacement of the entire TB (~$1050).

The TB assembly from a 01-02 Tundra is the same part number and maybe easier to locate used.

R&R covered in the FSM SF-35.

Possible causes

• defective part design (APPS part# has been "updated" 4x)
• dirty throttle body
• dirty throttle body possibly caused by EGR system
• bad electrical connections

During replacement it is recommended that you clean the throttle body.(FAQ - throttle body cleaning)
Consider replacing the starter contacts at the same time if you need to do them. You will have done some of the work needed to access the starter.

Some threads ....

Val678 – TPS/APPS problems in a 99 LX

DMX84 – TPS problems

EdsCruisin – APS problem possibly caused by build-up in the throttle body

EdsCruisin – APS problem and even i4c4lo suffers from TPS

TPS problem poll by rph1974 - Post up! Even you lurkers with no problems.

HI Trek - CEL code 'P1126' --> Magnetic clutch

PSDarmoured – TPS failure in a bad spot

calimaridog troubleshoots an electrical problem related to a starter job – fj55-100 explains dirty throttle body problems in post #11

Dealer wants to replace entire thottle body at $1400 - onesprung60 explains why and provides a "migrating grease" theory of TPS problems

Maingear troubleshoots a P1128 Throttle Control Motor Malfunction and Chad in Bangkok may be experiencing a TPS problem

TPS limp mode, now OK, fix or not? - Landpimp (Part # details from SinCity100)

loss of power? - AFRIKANZ struggles with "twit" dealers and a non-OBD2 EC market 100

yotor no motor

[ammodragon]

Thanks for all the info!

[e9999]

nice, thanks for taking the time.
have put it in faq