explanation for P0121?
Originally Posted by Darkhalf
ok well I just saw P0121 and that pertains to that particular thread as well.
are you sure, becuz i saw that it said only if P0121 isnt set? i have know idea, im just looking for help
thanks
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Teching In
Joined: Dec 2001
Posts: 387
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From: Southern IN, USA
P0121 TP sensor insufficient activity
Page 6-1445 from 2K shop manual.
TP sensor should be near 0.6 volt as idle and more than 4.0 V at WOT.
This code is set when predicted TP from other sensors does not equal the actual position as determined by the TPS voltage, for greater than 20 seconds, on the second consecutive occourance. Will automatically after 3 NON-occurances.
1. Inspect PCM harness and area around TPS and MAP sensor for debris or damage.
2. Monitor MAP sensor voltage when accellerating engine.
If it changes, MAP is OK.
If MAP does not change, Test MAP sensor with vacuum source for smooth and correct operation. (1 inch of vacuum = about 3.5kPa drop in MAP sensor reading as shown on a scan tool.) If not replace MAP sensor.
3. If MAP is OK, monitor TPS voltage with engine off, IGN on. It should show smooth and correct change in voltage as indicated on voltmeter or scan tool. If not, replace TPS sensor.
4. If TPS sensor responds correctly, inspect wiring harness for shorts, or poor connections, or other wiring or grounding problems. If none, replace PCM.
Now this assumes a stock engine and unmodified PCM programming. Anything beyond this is "uncharted territory".
The theory on this DTC is that a running engine, in 20 seconds of operation, is going to have SOME throttle inputs, and some sensors will show the need for this. If there are no ACTUAL throttle inputs as read by the TPS sensor, it sets a code.
Good luck!
MRK
Page 6-1445 from 2K shop manual.
TP sensor should be near 0.6 volt as idle and more than 4.0 V at WOT.
This code is set when predicted TP from other sensors does not equal the actual position as determined by the TPS voltage, for greater than 20 seconds, on the second consecutive occourance. Will automatically after 3 NON-occurances.
1. Inspect PCM harness and area around TPS and MAP sensor for debris or damage.
2. Monitor MAP sensor voltage when accellerating engine.
If it changes, MAP is OK.
If MAP does not change, Test MAP sensor with vacuum source for smooth and correct operation. (1 inch of vacuum = about 3.5kPa drop in MAP sensor reading as shown on a scan tool.) If not replace MAP sensor.
3. If MAP is OK, monitor TPS voltage with engine off, IGN on. It should show smooth and correct change in voltage as indicated on voltmeter or scan tool. If not, replace TPS sensor.
4. If TPS sensor responds correctly, inspect wiring harness for shorts, or poor connections, or other wiring or grounding problems. If none, replace PCM.
Now this assumes a stock engine and unmodified PCM programming. Anything beyond this is "uncharted territory".
The theory on this DTC is that a running engine, in 20 seconds of operation, is going to have SOME throttle inputs, and some sensors will show the need for this. If there are no ACTUAL throttle inputs as read by the TPS sensor, it sets a code.
Good luck!
MRK
WicketMike, I am assuming you are having this code after the TSP 231/237 cam install, correct? If so, I had it once, after doing the basic cam idle tune and set the idle to 1000cold, 900 warm. Tuned, started car, and bam code thrown. Restet it, none since. But, I am having some of the other problems we both posted on.
Have you reset and done an idle relearn? If not, Try it and see if it stops it.
Charlie.
Have you reset and done an idle relearn? If not, Try it and see if it stops it.
Charlie.
with ignition in on position, unplug the fuse for the PCM Batt and Ign in the main box, drvrs fender. wait a minute, then turn key off, plug fuses in, start and idle 5min, then ac on idle 5 min. It may help to drive for about 30miles or so as well, like after tuning for LTFTs since they will need to relearn.
I dont have anymore problems with P0120, but the early shifting into 2nd gear gets me pissed off everyonce in awhile.
I dont have anymore problems with P0120, but the early shifting into 2nd gear gets me pissed off everyonce in awhile.
TECH Fanatic
Joined: Mar 2003
Posts: 1,839
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From: La Porte, TX
how does p0121 relate to p1133 and p1153? I'm getting the bad o2 codes, as well as the TPS code. Will having the bad o2's cause the TPS code as well? I read all the tech jargon, but didn't quite get it. Also I just checked my IAC's with a Tech II and I'm down to 14 at opperating temp in park, and I'm bouncing between 40-50 in drive. Would any of this be related to the p0121 code?
Last edited by WS6snake-eater; Dec 23, 2003 at 02:32 PM.
Originally Posted by WS6snake-eater
how does p0121 relate to p1133 and p1153? I'm getting the bad o2 codes, as well as the TPS code. Will having the bad o2's cause the TPS code as well? I read all the tech jargon, but didn't quite get it. Also I just checked my IAC's with a Tech II and I'm down to 14 at opperating temp in park, and I'm bouncing between 40-50 in drive. Would any of this be related to the p0121 code?
im not sure, but i dont think P0121 would be related to bad 02's. maybe somebody else knows for sure. my iacs are over 100 at idle in park
Originally Posted by CAT3
WicketMike, I am assuming you are having this code after the TSP 231/237 cam install, correct? If so, I had it once, after doing the basic cam idle tune and set the idle to 1000cold, 900 warm. Tuned, started car, and bam code thrown. Restet it, none since. But, I am having some of the other problems we both posted on.
Have you reset and done an idle relearn? If not, Try it and see if it stops it.
Charlie.
Have you reset and done an idle relearn? If not, Try it and see if it stops it.
Charlie.
Charlie,
I only started having problems after the cam install.
its been about 150 miles since i changed the parameters for the code and it hasnt came on, now i just need to see if the problems it was causing have gone away, but i wont know until later this week. 
Which ones did you change, the Min & max MAP?
I hope it was it. I found out that my Po121 has been set, didnt lite me up, but the code was there last time I checked. Will clear again and see whats up. Keep me updated.
Charlie.
I hope it was it. I found out that my Po121 has been set, didnt lite me up, but the code was there last time I checked. Will clear again and see whats up. Keep me updated.
Charlie.
Originally Posted by CAT3
Which ones did you change, the Min & max MAP?
I hope it was it. I found out that my Po121 has been set, didnt lite me up, but the code was there last time I checked. Will clear again and see whats up. Keep me updated.
Charlie.
I hope it was it. I found out that my Po121 has been set, didnt lite me up, but the code was there last time I checked. Will clear again and see whats up. Keep me updated.
Charlie.
Yeah i changed the min & max for the parameters and i changed them from 55/65 to 75/85