Trying to check TPS voltage
- Thread starter mcate
- Start date
mcate
Registered User
Thanx Jerry, but I already trimmed the insulation back some & checked it. It read .91 VDC or so, so I think it's good. Codes I'm getting are 121 & 167, both leading me to the TPS. I didn't open the throttle up to see how much the voltage increases yet. Should I do that next?
Shockwave
Registered User
121 O/R/C Closed throttle voltage higher or lower than expected
167 R Insufficient throttle position change during Dynamic Response Test
During the Key On Engine Running (KOER) test there is a point when it calls for a dynamic response. Basically you have to stab the throttle quickly to full throttle then immediately let off. This does quite a few tests like test knock sensor among others and tests the TPS for change. You did not do it at the correct time so code 167 came up. This is just operator error during the test and nothing is wrong with the car.
Reread the proceedure for KEOR scan tests and try again. First clear the codes and then do a Key On Engine Off (KOEO) test and see if you have any codes. Then retest KOER.
Your tps of .91 volts is within range and shouldn't trip a code. I'm not convinced you have a problem.
Jerry
167 R Insufficient throttle position change during Dynamic Response Test
During the Key On Engine Running (KOER) test there is a point when it calls for a dynamic response. Basically you have to stab the throttle quickly to full throttle then immediately let off. This does quite a few tests like test knock sensor among others and tests the TPS for change. You did not do it at the correct time so code 167 came up. This is just operator error during the test and nothing is wrong with the car.
Reread the proceedure for KEOR scan tests and try again. First clear the codes and then do a Key On Engine Off (KOEO) test and see if you have any codes. Then retest KOER.
Your tps of .91 volts is within range and shouldn't trip a code. I'm not convinced you have a problem.
Jerry
mcate
Registered User
Thanx Jerry. Come to think of it, I didn't stab the throttle ALL the way when prompted. I only pressed it part way. I'll clear the codes & rerun the test today. I'm pretty sure the 167 will go away.
The 121 still has me puzzled, though. I've gotten it off & on since I put the 85mm TB on last year. The stock TPS wouldn't fit flush into the TB, so I had to purchase a different one. Bill at SCP gave me a part # for one that fits flush. The angle on the sensor where it grabs the "butterfly" on the TB looks the same as the OEM, so it should be working correctly. But I still get that 121 every so often.
The 121 still has me puzzled, though. I've gotten it off & on since I put the 85mm TB on last year. The stock TPS wouldn't fit flush into the TB, so I had to purchase a different one. Bill at SCP gave me a part # for one that fits flush. The angle on the sensor where it grabs the "butterfly" on the TB looks the same as the OEM, so it should be working correctly. But I still get that 121 every so often.
other problem?
the 121 can also be indicitave of a malfunction in the MAF. Basically it says that the MAF and TP are not agreeing with each other. It can be either a TP or MAF or a combo of both. Unmetered air leaks, sensor contamination, and or the disruption of the correct airflow over the MAF can all result in 121. A TP that is not returning to idle voltage or spiking up and down can also cause it. I guess my real point is that the TP is not the only cause for this code.
the 121 can also be indicitave of a malfunction in the MAF. Basically it says that the MAF and TP are not agreeing with each other. It can be either a TP or MAF or a combo of both. Unmetered air leaks, sensor contamination, and or the disruption of the correct airflow over the MAF can all result in 121. A TP that is not returning to idle voltage or spiking up and down can also cause it. I guess my real point is that the TP is not the only cause for this code.
Shockwave
Registered User
I'm guessing now:
My 1990 Ford Emission/Diagnosis book calls for tps voltage to be .8 volts of course the reference values can be +or- 20%. Try to get the voltage down to .8 or .85 and see if your problem goes away. The only thing I can think of is the EEC reading a little more voltage than you got at the tps. Maybe the circuit in the EEC is seeing higher value than your .91 volts. I beleive that anything over 1 volt is not considered idle by the EEC. If your butterfly is already as closed so as not to stick, you can elongate the holes on the TPS to get more adjustment if you need to.
Jerry
My 1990 Ford Emission/Diagnosis book calls for tps voltage to be .8 volts of course the reference values can be +or- 20%. Try to get the voltage down to .8 or .85 and see if your problem goes away. The only thing I can think of is the EEC reading a little more voltage than you got at the tps. Maybe the circuit in the EEC is seeing higher value than your .91 volts. I beleive that anything over 1 volt is not considered idle by the EEC. If your butterfly is already as closed so as not to stick, you can elongate the holes on the TPS to get more adjustment if you need to.
Jerry
mcate
Registered User
You know, after reading what YT90SC said, I'm starting to think that the problem might just be in the MAF instead. This all started when I put in a C&L 76mm MAF, along with the 85mm TB. After reading the thread at the bottom of this page entitled "Code 121 - TPS voltage inconsistent with MAF". I'm wondering if my problem would go away with a larger MAF sampling tube, or maybe trying a different MAF, or MAF electronics? Just a thought.
mcate
Registered User
Well, the 1st thing I'm going to do is replace at least the passenger side O2 sensor & fix the code 172 I'm getting. Hope to do that tomorrow morning. Might then swap the MAF electronics out with my other '95 SC & see if that works. I'll also drill out the holes in the TPS & try to adjust it down a little.
Thanx for all the help guys. Much appreciated.
Mike
Thanx for all the help guys. Much appreciated.
Mike
Shockwave
Registered User
You never mentioned code 172 !!!!!!!!!!!!!
In January we picked up a 91 SC for $1200 , I was getting codes:
121 O/R/C Closed throttle voltage higher or lower than expected
176 C Lack of Oxygen Sensor (HEGO) switches, indicates lean (LEFT SIDE)
543 O/C Fuel pump secondary circuit failure
From doing some research the fuel pump circuit is the same as the heater circuit on the O2 sensor. So the bad O2 caused 543 as well. We also had a bad IAC that wouldn't let the car idle down below 2000 rpm. I replaced the O2 and the IAC and all the codes went away.
Jerry
In January we picked up a 91 SC for $1200 , I was getting codes:
121 O/R/C Closed throttle voltage higher or lower than expected
176 C Lack of Oxygen Sensor (HEGO) switches, indicates lean (LEFT SIDE)
543 O/C Fuel pump secondary circuit failure
From doing some research the fuel pump circuit is the same as the heater circuit on the O2 sensor. So the bad O2 caused 543 as well. We also had a bad IAC that wouldn't let the car idle down below 2000 rpm. I replaced the O2 and the IAC and all the codes went away.
Jerry
mcate
Registered User
Sorry I didn't tell you about the 172, Jerry! I figured it was pretty much a no-brainer. Same symptoms my other '95 had when the O2 sensors went bad: mileage getting really crappy, & code 172. Just put a $140 worth of Bosch sensors on it & cleared the codes. Took it out for a drive &, so far, no CE light. Gotta go to work here in a bit, so I'll check for the 121, & any other codes tomorrow.