TPS readings
10-24-2009 | 02:21 PM
#1
Thread Starter
Member
Joined: Oct 2009
Posts: 108
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Year: 1989
Model: Cherokee
Engine: 4.0L I6
TPS readings
I've been having problems lately with terrible fuel economy (roughly 5-10 MPG) on my '89 XJ, so I decided to clean out the throttle body, IAC and check the TPS. IAC looks brand new, and so does the TPS. The weird thing is the readings I got off of the TPS though...
I used this site as a guide as I've never tested a TPS before. According to the guide, the output voltage divided by the input voltage should equal .830 V (+ or - .005 V). My readings for output voltage were 4.60 V (TPS rotated clockwise as far as possible) and 4.47 V (TPS rotated counterclockwise as far as possible). Input voltage was 4.67 V at all positions. This would put me at .957 V output over input best case scenario. Am I missing something here or is the sensor just bad?
I used this site as a guide as I've never tested a TPS before. According to the guide, the output voltage divided by the input voltage should equal .830 V (+ or - .005 V). My readings for output voltage were 4.60 V (TPS rotated clockwise as far as possible) and 4.47 V (TPS rotated counterclockwise as far as possible). Input voltage was 4.67 V at all positions. This would put me at .957 V output over input best case scenario. Am I missing something here or is the sensor just bad?
10-24-2009 | 08:32 PM
#3
I like it in the dirt
Joined: Jul 2009
Posts: 1,802
Likes: 1
From: Alberta Canada
Year: 2003
Model: Grand Cherokee
Engine: 4.0
LoL probably too technical for most of us, if things go awry, i just ask people on here what it is, and try suggestions starting with the cheapest one
10-25-2009 | 04:50 AM
#4
Member
Joined: May 2009
Posts: 134
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Year: 1989
Model: Cherokee
Engine: straight 6
google it a bit there i thought not sure but it might of been 5.50 on my 89 xj its kind of complicated i know you have to get 2 numbers off and devide it but i did replace the tps after it wasnt putting out the voltage i needed and it worked great after words there about 60bucks at auto zone the bottom screw is for major adjustments and the top screw is for pin point adjustments the new tps does come with new screws if this helps at all sorry i dont have the link anymore for the adjustments but your on the right track
10-25-2009 | 02:23 PM
#5
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Joined: Oct 2009
Posts: 108
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Year: 1989
Model: Cherokee
Engine: 4.0L I6
Yeah, I've already spent about an hour looking around the web for answers to this one...
I think I'll see if O'reillys will let me buy a TPS and return it if that has weird readings also.
I think I'll see if O'reillys will let me buy a TPS and return it if that has weird readings also.
10-25-2009 | 04:11 PM
#6
Thread Starter
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Joined: Oct 2009
Posts: 108
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Year: 1989
Model: Cherokee
Engine: 4.0L I6
Well they didn't like that idea very much 
I'll call around to junkyards on Monday to see about maybe picking one up out there. One thing that seems kind of funny to me though is the input voltage. It should be a 5.0 V supply, and it is on different sensors that I've tested, but for the TPS the supply is only 4.67 V. Any ideas on why this would be?
I'll call around to junkyards on Monday to see about maybe picking one up out there. One thing that seems kind of funny to me though is the input voltage. It should be a 5.0 V supply, and it is on different sensors that I've tested, but for the TPS the supply is only 4.67 V. Any ideas on why this would be?
10-25-2009 | 04:27 PM
#7
CF Veteran
Joined: Aug 2009
Posts: 1,127
Likes: 12
From: 9000 ft, CO
Year: 1999 XJ
Model: Cherokee
Engine: I6 4.0L
There's not enough variance between those readings, I would say the sensor is bad. It should should drop more at WOT and be closer to 5v (at least 4.8) at idle.
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10-27-2009 | 10:20 PM
#11
Member
Joined: May 2009
Posts: 134
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Year: 1989
Model: Cherokee
Engine: straight 6
mine was reading a 4.6 or something also and i changed it out worked fine my truck wouldnt let the tranny shift intill 4200rpms on all gears i found this on another post this is what i used to fix the issue and yes mine was an 89 xj
THROTTLE POSITION SENSOR (TPS)
NOTE: Adjustment of TPS only applies to the 4.0L models. It may be
necessary to remove throttle body from intake manifold, to
access sensor wiring harness.
Checking & Adjusting - 4.0L (Automatic Transmission)
1) Locate the square TPS connector. Note connector terminal
identification stamped on the back of the connector. Turn ignition on.
2) Connect voltmeter through back of wiring harness
connector. Connect negative voltmeter lead to terminal "D" and
positive voltmeter lead to terminal "A" to check input voltage. DO NOT
disconnect TPS connector.
3) Hold throttle plate closed against idle stop and note
voltage. Input voltage should be approximately 5 volts. Disconnect
voltmeter positive lead and connect to terminal "B" to measure output
voltage.
4) With throttle plate closed, measure the output voltage.
The output voltage should be approximately 4.2 volts. If output
voltage is not within specification, loosen TPS retaining screws.
5) Partially tighten one retaining screw. Rotate TPS to
obtain correct output voltage. Tighten retaining screws once correct
voltage is obtained.
Checking & Adjusting - 4.0L (Manual Transmission)
1) Turn ignition on. Connect voltmeter through back of wiring
harness connector. Connect negative voltmeter lead to terminal
"B" and positive voltmeter lead to terminal "A". DO NOT disconnect TPS
connector.
2) Hold throttle plate in the closed throttle position
against idle stop and note input voltage reading. Input voltage should
be approximately 5.0 volts.
3) Disconnect positive lead from terminal "A" and connect to
terminal "C" to check output voltage. Output voltage should be checked
with throttle plates fully closed.
4) Output voltage should be approximately 0.8 volts. If
output voltage is not within specification, loosen TPS bottom
retaining screw and pivot sensor for a large adjustment or top
retaining screw for a fine adjustment.
5) Adjust sensor to obtain correct output voltage. Tighten
retaining screws. Remove voltmeter.
necessary to remove throttle body from intake manifold, to
access sensor wiring harness.
Checking & Adjusting - 4.0L (Automatic Transmission)
1) Locate the square TPS connector. Note connector terminal
identification stamped on the back of the connector. Turn ignition on.
2) Connect voltmeter through back of wiring harness
connector. Connect negative voltmeter lead to terminal "D" and
positive voltmeter lead to terminal "A" to check input voltage. DO NOT
disconnect TPS connector.
3) Hold throttle plate closed against idle stop and note
voltage. Input voltage should be approximately 5 volts. Disconnect
voltmeter positive lead and connect to terminal "B" to measure output
voltage.
4) With throttle plate closed, measure the output voltage.
The output voltage should be approximately 4.2 volts. If output
voltage is not within specification, loosen TPS retaining screws.
5) Partially tighten one retaining screw. Rotate TPS to
obtain correct output voltage. Tighten retaining screws once correct
voltage is obtained.
Checking & Adjusting - 4.0L (Manual Transmission)
1) Turn ignition on. Connect voltmeter through back of wiring
harness connector. Connect negative voltmeter lead to terminal
"B" and positive voltmeter lead to terminal "A". DO NOT disconnect TPS
connector.
2) Hold throttle plate in the closed throttle position
against idle stop and note input voltage reading. Input voltage should
be approximately 5.0 volts.
3) Disconnect positive lead from terminal "A" and connect to
terminal "C" to check output voltage. Output voltage should be checked
with throttle plates fully closed.
4) Output voltage should be approximately 0.8 volts. If
output voltage is not within specification, loosen TPS bottom
retaining screw and pivot sensor for a large adjustment or top
retaining screw for a fine adjustment.
5) Adjust sensor to obtain correct output voltage. Tighten
Last edited by thesundancekid; 10-27-2009 at 10:29 PM.
10-27-2009 | 10:45 PM
#12
Thread Starter
Member
Joined: Oct 2009
Posts: 108
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Year: 1989
Model: Cherokee
Engine: 4.0L I6
Yeah, I read around a bit more and found that input voltages down to 4.5V aren't that uncommon. I can't find anything on ebay, and I haven't gone around to junkyards yet checking for one. I'll update when I get a new one and let you know how it works.
10-28-2009 | 11:16 PM
#13
Junior Member
Joined: Sep 2009
Posts: 86
Likes: 0
From: Saskatoon, SK
Year: 1988
Model: Cherokee
Engine: 4.0L
I found this site really helpful;
http://www.lunghd.com/Tech_Articles/...iagnostics.htm
hope it helps.
http://www.lunghd.com/Tech_Articles/...iagnostics.htm
hope it helps.
10-29-2009 | 10:33 AM
#15
Renix Super Guru
Joined: Mar 2008
Posts: 24,653
Likes: 19
From: In yourz postez fissin jurr spelinzs
Year: 1990XJ/1989MJ
Model: Comanche
Engine: 4.0L Renix
I found this site really helpful;
http://www.lunghd.com/Tech_Articles/...iagnostics.htm
hope it helps.
http://www.lunghd.com/Tech_Articles/...iagnostics.htm
hope it helps.
And yes I am a Renix Guru.