Engine code p0121
03-19-06, 08:47 PM
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Engine code p0121
Can someone give me some help? I have 65k miles on my 2000 RX300 and recently the check enine light came on. I went to autozone and had them scan my car and got a "TP sensor p0121" code. I repleced the TP sensor but the check engine light is still on. I scanned the car again and it still has the same code. How do I clear the check engine light without going to the dealer?
03-19-06, 09:54 PM
#2
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Pull the EFI fuse in the fusebox for a few seconds, it is a yellow 20 AMP fuse and there is a diagram underneath the fusebox cover. Pulling the negative battery terminal will also do this, but erase a lot of memory settings (radio, seat, clock), but EFI will not.
Let me know if you experience further trouble on this, as I was reading about the P0121 error in the service manual and it may be something in the throttle body butterfiles or the ECM after chaning the the throttle position sensor like you did.
Let me know if you experience further trouble on this, as I was reading about the P0121 error in the service manual and it may be something in the throttle body butterfiles or the ECM after chaning the the throttle position sensor like you did.
03-20-06, 02:21 PM
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Hey,
Thanks for the tip. I went under the hood and pulled the EFI fuse and the check engine light is now off. So far it has not come back on. At first, I disconnected the battery when I replaced the TPS sensor and the check engine light turned off for about 50-100 miles then it would come back on. I hope it stays off now.
Thanks for the tip. I went under the hood and pulled the EFI fuse and the check engine light is now off. So far it has not come back on. At first, I disconnected the battery when I replaced the TPS sensor and the check engine light turned off for about 50-100 miles then it would come back on. I hope it stays off now.
03-25-06, 05:02 PM
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Ugghhhhh! The check engine light is back on. I went back to Autozone and it's the same p0121 code. I replaced the throttle body sensor and pulled the EFI fuse but the lcheck engine light is back after a week of driving. Help please...
03-25-06, 05:42 PM
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OK.
I don't know if I can give you a precise answer.
Let's first discuss what P0121 is: Throtte/Pedal/Position Sensors/Switch "A" Circuit Range/Performance Problem.
That last point is key as the twin code is P0120 where the only difference in the last words are Circuit Malfunction.
First, is P0121 the only code you are getting?
What causes P0121 to occur it that after your RX goes over about 19 mph, the throttle position sensor is out of range (could be for just an instant). Now, the manual has one page under P0121 and nothing else and the only recourse I see under that code is replacing the sensor. Another way to read this, is the ECM thinks the throttle body valve openings should be at one angle and in fact they are not in reality.
When I looked under P0120, the only things I could get as far as problem areas are the following:
1. ECM (not likely)
2. Throttle position sensor (not likely since you just installed a new one)
3. Harness between between ECM and throttle position sensor (possible as I would check the connection only on the sensor)
4. I read a lot in this section under P0120 about the throttle valve being fully open. If I were in this position, I would take off the two black baffles (they are after the MAF sensor, rubber pieces that hook on to the throttle body), then pull the accelerator cable (or have someone push on the accelerator) and see that the throttle body butterflies are opening and closing correctly.
One thing that comes to mind since I have played with the accelerator cord (all too much as many of you have read in my previous posts) is that it might be a little loose.
In my column, "Ramming Speed" I describe how to tighten the cord on page 2, https://www.clublexus.com/forums/sho...celerator+cord
P0120 also mentions to check the voltages on the sensor connections and on the ECM where the sensor hooks up, but this is in relation to P0120, not P0121.
Although it is not mentioned in the manual, I also get a hunch the infamous MAF sensor could be at play (this does happen in other vehicles with relation to P0121). Check to see that the red diode is clean along with the resistors as talked about in, https://www.clublexus.com/forums/sho...ght=MAF+sensor
Let me know on the MAF and also on the throttle body valve openings.
I don't know if I can give you a precise answer.
Let's first discuss what P0121 is: Throtte/Pedal/Position Sensors/Switch "A" Circuit Range/Performance Problem.
That last point is key as the twin code is P0120 where the only difference in the last words are Circuit Malfunction.
First, is P0121 the only code you are getting?
What causes P0121 to occur it that after your RX goes over about 19 mph, the throttle position sensor is out of range (could be for just an instant). Now, the manual has one page under P0121 and nothing else and the only recourse I see under that code is replacing the sensor. Another way to read this, is the ECM thinks the throttle body valve openings should be at one angle and in fact they are not in reality.
When I looked under P0120, the only things I could get as far as problem areas are the following:
1. ECM (not likely)
2. Throttle position sensor (not likely since you just installed a new one)
3. Harness between between ECM and throttle position sensor (possible as I would check the connection only on the sensor)
4. I read a lot in this section under P0120 about the throttle valve being fully open. If I were in this position, I would take off the two black baffles (they are after the MAF sensor, rubber pieces that hook on to the throttle body), then pull the accelerator cable (or have someone push on the accelerator) and see that the throttle body butterflies are opening and closing correctly.
One thing that comes to mind since I have played with the accelerator cord (all too much as many of you have read in my previous posts) is that it might be a little loose.
In my column, "Ramming Speed" I describe how to tighten the cord on page 2, https://www.clublexus.com/forums/sho...celerator+cord
P0120 also mentions to check the voltages on the sensor connections and on the ECM where the sensor hooks up, but this is in relation to P0120, not P0121.
Although it is not mentioned in the manual, I also get a hunch the infamous MAF sensor could be at play (this does happen in other vehicles with relation to P0121). Check to see that the red diode is clean along with the resistors as talked about in, https://www.clublexus.com/forums/sho...ght=MAF+sensor
Let me know on the MAF and also on the throttle body valve openings.
03-25-06, 05:57 PM
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I will check the MAF sensor and use electrical cleaner to clean the red diode. In addition, I think I'll try to clea out the throttle body. I'll let you know if it works. Thanks for the reply.
11-07-17, 12:37 PM
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VSC, Check Engine Light, engine hesitates. Hard Brake Pedal
Howdy all... Code only shows P0121 from Auto Zone scanner. TPS etc. Replaced TPS. Disconnected both sides of batter toclear code. 30 minutes after driving, Hesitation during acceleration returned (Idles okay) VSC, Ck Engine light on and hard brake pedal when slowing to stop. Check all fuses. All good. Also checked MAF by disconnecting while engine running. Stalled engine a as expected if MAF working right.
Also researched about Oil Control Valve Engine Timing Solenoid issues, robbing vacuum from brake booster also causing hesitation and activating the above lights mentioned on dash. It relates to sludge. Although I run Synthetic oil which is very clean. For the inexpensive cost I found on the internet, I've ordered Right + Left Oil Control Valve Engine Variable Timing Solenoid VVT For Toyota I dislike guessing games and tossing money after parts. I spent 9 years as a used car service manager at a large dealership and know this can also happen and become very expensive for a car with 181,000 miles on it. Suggestions gladly accepted.
Also researched about Oil Control Valve Engine Timing Solenoid issues, robbing vacuum from brake booster also causing hesitation and activating the above lights mentioned on dash. It relates to sludge. Although I run Synthetic oil which is very clean. For the inexpensive cost I found on the internet, I've ordered Right + Left Oil Control Valve Engine Variable Timing Solenoid VVT For Toyota I dislike guessing games and tossing money after parts. I spent 9 years as a used car service manager at a large dealership and know this can also happen and become very expensive for a car with 181,000 miles on it. Suggestions gladly accepted.
Last edited by GVRoots; 11-07-17 at 12:41 PM.
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11-07-17, 08:46 PM
#8
Howdy all... Code only shows P0121 from Auto Zone scanner. TPS etc. Replaced TPS. Disconnected both sides of batter toclear code. 30 minutes after driving, Hesitation during acceleration returned (Idles okay) VSC, Ck Engine light on and hard brake pedal when slowing to stop.
"90% of the time when you have a TPS code the TPS is not the problem..."
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