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Why would TPS signal wire have 4.8 volts coming from the ECM?

Tiny
PELWYNF2009
  • MEMBER
  • 2000 DODGE NEON
  • 165,000 MILES
Is there a limp mode that does this or is it a short coming out of the ECM? My understanding is that this wire is read by the computer and there isn't supposed to be voltage coming out of the computer through it. I'm not sure if the car will do this for a reason or if I have a short.

I get the same results with two different computers so I'm pretty sure it's not the problem. Should I start testing every plug on the car with an ohm meter to find a short. I have been digging on this for quite some time... Please help.
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Monday, April 23rd, 2012 AT 12:18 AM

7 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Computer sends a 5 volt signal down the line to the sensor. There is a ground wire and a sensor return wire back to the pcm. I would disconnect the oxygen sensor because if the heaters short inside the sensor it will cause the PCM to drop voltage.

Roy
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Monday, April 23rd, 2012 AT 12:22 AM
Tiny
PELWYNF2009
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I understand, when the sensor is unhooked the sensor return wire reads 4.8 volts from the computer. 5 volt supply wire and ground wire are normal.
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Monday, April 23rd, 2012 AT 12:26 AM
Tiny
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That is normal also.

Roy
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Monday, April 23rd, 2012 AT 12:36 AM
Tiny
PELWYNF2009
  • MEMBER
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So, testing the tps plug with the key on and the tps unhooked I have 5 volts, 4.8 volts, and ground. That's normal? Why would the computer send 4.8 volts out the signal wire. Shouldn't that wire be an input to the comp not an output?
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Monday, April 23rd, 2012 AT 12:58 AM
Tiny
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The return signal when hooked up will lower the voltage back to the pcm.

Roy
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Monday, April 23rd, 2012 AT 12:59 AM
Tiny
PELWYNF2009
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I noticed that earlier. I did find one wire going to the oxygen sensor melted so once I fixed that it works normally. Thanks.
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Monday, April 23rd, 2012 AT 1:04 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Use 2CarPros anytime, we are here to help. Please tell a friend.
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Monday, April 23rd, 2012 AT 1:05 AM

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