TPS gone kaput, threw a CEL
09-08-2004, 01:25 PM
#11
Registered User
Thread Starter
Jim at ProFlow Design was kind enough to set me up with a TPS in the S2000 range. I just replaced it, with mixed results.
Previously, the CEL would immediately come on with the engine starting up (after an ECU reset). With the replaced TPS, no CEL so far (drive about 10 miles, turned the car on/off about 10-15 times), so that's good.
However, the car still stalls... this time, though, it seems like it wants to stall even while I'm in motion. Idle is a bit lower than normal, so I do not know if that due to the different TPS or something else (the TPS is pretty much in line with the values measured from the original one). Since there's no CEL, there's no code for me to pull. Makes me wonder if the MAP is telling me it finally needs to be replaced rather than beaten, so if I get the chance I'll try to swap MAPs with someone and try it again.
Suggestions welcome...
Previously, the CEL would immediately come on with the engine starting up (after an ECU reset). With the replaced TPS, no CEL so far (drive about 10 miles, turned the car on/off about 10-15 times), so that's good.
However, the car still stalls... this time, though, it seems like it wants to stall even while I'm in motion. Idle is a bit lower than normal, so I do not know if that due to the different TPS or something else (the TPS is pretty much in line with the values measured from the original one). Since there's no CEL, there's no code for me to pull. Makes me wonder if the MAP is telling me it finally needs to be replaced rather than beaten, so if I get the chance I'll try to swap MAPs with someone and try it again.
Suggestions welcome...
09-08-2004, 01:35 PM
#12
Registered User
Thread Starter
I just noticed a quick note from Jim on the invoice mentioning setting the TPS to match my original TPS resistance. The original piece had a lower resistance of 648 ohms, whereas the new one is much closer to 400 ohms.
Are the TPSs adjustable, and if so, how? Would the lower resistance cause the stalling issue I'm seeing? If so, and the TPS isn't adjustable, I'll place a 250 ohm resistor in series with the return line... should have little effect, if any, on WOT.
Are the TPSs adjustable, and if so, how? Would the lower resistance cause the stalling issue I'm seeing? If so, and the TPS isn't adjustable, I'll place a 250 ohm resistor in series with the return line... should have little effect, if any, on WOT.
09-08-2004, 02:32 PM
#13
Former Moderator
The TPS has slotted screw holes. If the original tamper proof screws have been replaced, you can "adjust" the TPS. A common trick on 5.0L Mustangs was to advance the TPS to read as close to 5.0V at WOT as possible. Closed throttle Volts should be .5V, WOT should be 4.5V You can either monitor the TPS Voltage with a OBDII scan tool, Or a meter. You can backprobe the TPS connectors Red/black wire. Just rememer key on, engine off while testing.
Seeing your original TPS was bad, I wouldn't use it's resistance to compare with a new one.
Seeing your original TPS was bad, I wouldn't use it's resistance to compare with a new one.
09-08-2004, 03:07 PM
#14
Registered User
Thread Starter
Slow, You ,ay have something there, but I can't say for sure yet. I was looking at the original TPS and noticed the slots... remembering I had to twist the TPS slightly to match up the notches/levers inside, I though this may be the key. So, I just came back up from the garage after a readjustment.
I remeasured the TPS as it was currently sitting... I was reading nearly 1kohm, so a lot higher, not lower, than I originally thought. My original TPS read 648 ohms at idle, so with some twisting of the new TPS, I was able to get mid-600s, so close enough.
The engine turned over, but it immediately threw the CEL and started stalling again.
Here's an interesting tidbit, though. If I tap the pedal to rev the engine and let the rpms drop, the rpms drop to about 900, I distinctly hear a 'click' (like the sound heard when the air pump turns on), the rpms jump up to 1200-1300 for about 2 seconds, then it proceeds to drop out and stall. The click and rpm jump is repeatable every time.
The ONLY thing I can think of at this point is the 648 ohms I read off of the original TPS is incorrect. The only data I have to back up that theory is the CEL. The old TPS read 648 ohms and threw a CEL every time. Installing a new TPS, 'improperly' adjusted to show nearly 1kohm, never threw a CEL with 10+ miles of driving and 10-15 on/off cycles. Adjusting the new TPS to original TPS value of 648 ohms immediately throws a CEL.
I will go back and measure the voltage at the pins, rather than the resistance to see what I get, but if that doesn't pan out, I'm out of ideas.
Very frustrating... at this point it looks like I'll have to take it to Honda and let the techs there have a whack at it.
I remeasured the TPS as it was currently sitting... I was reading nearly 1kohm, so a lot higher, not lower, than I originally thought. My original TPS read 648 ohms at idle, so with some twisting of the new TPS, I was able to get mid-600s, so close enough.
The engine turned over, but it immediately threw the CEL and started stalling again.
Here's an interesting tidbit, though. If I tap the pedal to rev the engine and let the rpms drop, the rpms drop to about 900, I distinctly hear a 'click' (like the sound heard when the air pump turns on), the rpms jump up to 1200-1300 for about 2 seconds, then it proceeds to drop out and stall. The click and rpm jump is repeatable every time.
The ONLY thing I can think of at this point is the 648 ohms I read off of the original TPS is incorrect. The only data I have to back up that theory is the CEL. The old TPS read 648 ohms and threw a CEL every time. Installing a new TPS, 'improperly' adjusted to show nearly 1kohm, never threw a CEL with 10+ miles of driving and 10-15 on/off cycles. Adjusting the new TPS to original TPS value of 648 ohms immediately throws a CEL.
I will go back and measure the voltage at the pins, rather than the resistance to see what I get, but if that doesn't pan out, I'm out of ideas.
Very frustrating... at this point it looks like I'll have to take it to Honda and let the techs there have a whack at it.
09-08-2004, 03:21 PM
#16
Registered User
Thread Starter
...and things continue to get more wierd...
Just checked the voltage at the sensor. 0.23V at WOT and essentially 0V at idle. I checked multiple times to make sure I had the correct wires (bottom 2).
Those readings make no sense when you consider the engine runs fine as long as you don't try to idle, but they would certainly make the CEL go on. I doubt two TPSs are bad, so it makes me think something else is up.
Just checked the voltage at the sensor. 0.23V at WOT and essentially 0V at idle. I checked multiple times to make sure I had the correct wires (bottom 2).
Those readings make no sense when you consider the engine runs fine as long as you don't try to idle, but they would certainly make the CEL go on. I doubt two TPSs are bad, so it makes me think something else is up.
09-08-2004, 04:12 PM
#18
Registered User
Join Date: Aug 2002
Location: Come see me after class.
Posts: 20,840
Likes: 0
Received 0 Likes
on
0 Posts
P0122 is "TPS Low Input." Your TPS isn't getting the full reference voltage.
The only value the ECU reads from TPS is voltage, not resistance. Resistance has nothing to do with it.
Looking at the "back" of the connector (the wires are are facing you), there should be three wires (from the left):
1) green/yellow: ground
2) red/black: signal voltage (output)
3) yellow/blue: reference voltage (input)
Check your reference voltage. I bet you're not getting the full 5 volts. Trace it back down with voltage drops at each connection from the TPS back, and see if you can find the problem. This would explain the higher resistance though; less voltage = more resistance.
The only value the ECU reads from TPS is voltage, not resistance. Resistance has nothing to do with it.
Looking at the "back" of the connector (the wires are are facing you), there should be three wires (from the left):
1) green/yellow: ground
2) red/black: signal voltage (output)
3) yellow/blue: reference voltage (input)
Check your reference voltage. I bet you're not getting the full 5 volts. Trace it back down with voltage drops at each connection from the TPS back, and see if you can find the problem. This would explain the higher resistance though; less voltage = more resistance.
09-08-2004, 04:17 PM
#19
Registered User
Join Date: Aug 2002
Location: Come see me after class.
Posts: 20,840
Likes: 0
Received 0 Likes
on
0 Posts
BTW, when you have a faulty component (TPS) the ECU will bypass it and reference a similar component, such as MAP. This could explain the rough idle and the click/rev on tip-in.
Also, depending on which scanner you're using, a voltage reading of TPS may not be accurate... or precise. TPS has to be absolutely 100% steady and lesser scan tools are simply not capable of reading such quick/small variations (i.e. slow refresh rate). A better tool to diagnose TPS would be a scope.
Also, depending on which scanner you're using, a voltage reading of TPS may not be accurate... or precise. TPS has to be absolutely 100% steady and lesser scan tools are simply not capable of reading such quick/small variations (i.e. slow refresh rate). A better tool to diagnose TPS would be a scope.
09-08-2004, 04:19 PM
#20
Registered User
Join Date: Aug 2002
Location: Come see me after class.
Posts: 20,840
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by MacGyver,Sep 8 2004, 06:21 PM
...and things continue to get more wierd...
Just checked the voltage at the sensor. 0.23V at WOT and essentially 0V at idle. I checked multiple times to make sure I had the correct wires (bottom 2).
Those readings make no sense when you consider the engine runs fine as long as you don't try to idle, but they would certainly make the CEL go on. I doubt two TPSs are bad, so it makes me think something else is up.
Just checked the voltage at the sensor. 0.23V at WOT and essentially 0V at idle. I checked multiple times to make sure I had the correct wires (bottom 2).
Those readings make no sense when you consider the engine runs fine as long as you don't try to idle, but they would certainly make the CEL go on. I doubt two TPSs are bad, so it makes me think something else is up.