Codes P0500 and P1500

JAEDAV12

MEMBER
1998 FORD EXPEDITION
5.4L
V8
2WD
AUTOMATIC
88,944 MILES

So at first it threw the p0500 code. So I checked the connector for voltage and the voltage was there. There were no signs of corrosion or breaks in the wires. So then I replaced the sensor problem still exists. Then it threw the P1500 code so I checked the sensor in the transmission for resistance and the connector for the 5 voltage reference and that checked out good. The problem only exists when the transmission is cold, once it warms up the truck rides like normal. Can anyone help?

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

I am going to provide the diagnostics for both P0500 and P1500. Let me know if this is how you checked the system. Also, let me know what the symptoms are you experience.

Take care,
Joe

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Monday, November 2nd, 2020 AT 5:54 PM

KASEKENNY

MECHANIC
18,907 POSTS

Okay. This is telling you that the issue is intermittent and if the issue is only there when the vehicle is cold then this is when we need to make all the tests. We need to test the signal when this is happening to see what it is telling the the PCM. Assuming you don't have a scan tool and since you already replaced the sensor, if it were me I would run a new wire to the sensor and run a new ground and retest it. This would eliminate all wiring issues. If it still acts up then it is most likely just the PCM causing the issue.

Take a look at this info and let me know what questions you have.

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Monday, November 2nd, 2020 AT 6:02 PM

JAEDAV12

MEMBER
46 POSTS

The symptoms I’m experiencing are harsh shifts, no speed being displayed and sometimes it’ll just start increasing the rpm and the vehicle doesn’t move then it’ll kick into gear and start moving.

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Monday, November 2nd, 2020 AT 6:17 PM

JAEDAV12

MEMBER
46 POSTS

Kasekenny would you run new wires from the PCM or just from where the wires join into the harness?

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Monday, November 2nd, 2020 AT 6:18 PM

KASEKENNY

MECHANIC
18,907 POSTS

I would go straight from the PCM to the sensor. So you can just take a T pin or safety pin in the back of the PCM connector and then the same on the sensor. Cut the existing wire at both ends about 5 inches from the connectors so it eliminates the existing wire but leaves you room to fix it if this was not the issue. Then just use a test wire with alligator clips on each end and clip it to the T pins. This is the quickest and easiest way to prove wiring is or is not the issue. The ground wire can just be a redundant wire but could be done second. This way you know of it is the signal or ground wire.

Let me know if you have questions. Take a look at the attachment.

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