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Daniel Wilson
Daniel Wilson,
Category: Ford
Satisfied Customers: 5586
Experience:  Owner at DJ Wilson
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After lots of time and money I'm still where I started. Temp

Customer Question

After lots of time and money I'm still where I started. Temp gauge in trk. Will not work. So no ac. I've changed the sending unit.the pcm , the instrument cluster and a pint of blood. There us no voltage coming out of the pin for the sending unit. After the trk warms up and you turn the key on the gauge wI'll register where it's suppose to. As soon as you start the engine the buzzer sounds and check gauge warning cones on. Gauge falls past cool....please help
Submitted: 2 months ago.
Category: Ford
Expert:  Kenny Z. replied 2 months ago.

Hello, my name is***** and thanks for your question.

Engine size? 4.2L, 4.6L, 5.4L? Is it setting codes also in the PCM like P0116, P0119, P0125, P0128, P1116, P1285, P1288, P1289, P128A, P1290, or P1299?

Customer: replied 2 months ago.
5.4...only code in getting is cylinder head temp
Expert:  Kenny Z. replied 2 months ago.

Ok thanks. Those are all CHT codes. Any of them in particular?

Customer: replied 2 months ago.
P 1289
Expert:  Kenny Z. replied 2 months ago.

Do you have the intake off or is it all together?

Customer: replied 2 months ago.
All back together now. I get no voltage coming on the yellow and blue signal wire... even on the pin at the pxm
Expert:  Kenny Z. replied 2 months ago.

No voltage would indicate a short to ground in the wiring.

Customer: replied 2 months ago.
how would I find it. .
Expert:  Kenny Z. replied 2 months ago.

Usually with this code and symptom, its usually a wiring issue where the harness routes through the rear of the intake near the IMRC actuators. Has the wiring been thoroughly inspected in this area? If the intake was ever removed and the wiring was not was not routed exactly as from the factory or if all of the support clips not installed properly it will rub on the IMRC actuator rods causing a short. With the intake on its next to impossible to inspect. This all I have ever seen for this isuue. I have also seen rodent damage in that same area as they like to build nests in the valley.

If you are satisfied with your answer, please take a moment to rate my service as you see fit. Experts are not compensated without a positive rating. Providing a rating does not close the question, you can reply or ask additional questions without incurring further charges.

Customer: replied 2 months ago.
Nor the case here. I have replaced the wiring from the sensor to the pcm. Checked and double checked.
Expert:  Kenny Z. replied 2 months ago.

Do you have a scanner that can monitor/display PCM data?

Customer: replied 2 months ago.
I think it will
Expert:  Kenny Z. replied 2 months ago.

The signal return for the CHT does not wire directly to the PCM, it goes to a splice where 10 wires join, then to the PCM. How did you account for that? My diagram shows the signal wire as yellow and light green stripe and signal return (ground) as gray/red stripe. Are these the same colors you have?

Customer: replied 2 months ago.
the same colors. I checked the continuity on several of the sensors on the return signal wire
Expert:  Kenny Z. replied 2 months ago.

Yes but where exactly did you connect the new signal return wire from the cht?

Customer: replied 2 months ago.
just pass the connection so as not to compromise the rest of the return wires
Expert:  Kenny Z. replied 2 months ago.

OK, back to scanner. Key on engine off what is the data for the cht showing in temp and voltage? What is the EOT showing for temp and voltage? With the engine started and the fault occurs what is the data for the cht showing in temp and voltage? What is the EOT showing for temp and voltage?

Customer: replied 2 months ago.
Hang on I'll check
Expert:  Kenny Z. replied 2 months ago.

OK

Customer: replied 2 months ago.
I did not see on my scanner where that info. Is. Only paid 100 bucks so maybe I got what I paid for
Expert:  Kenny Z. replied 2 months ago.

OK. You eliminated (cut) the 2 original wires correct not splice in and overlay correct? New pigtail on the CHT?

Customer: replied 2 months ago.
sir
Expert:  Kenny Z. replied 2 months ago.

If you disconnect the PCM connector and measure resistance across pins 41 and 58 what do you get? With the PCM still disconnected what resistance do you get from pin 41 to battery ground?

Customer: replied 2 months ago.
It started with temp gauge working on an off while driving. It would beep and drop. Then it stopped working all together. But like I said the gauge will register after the trk warms up until you start it. Then it quits. Why wouldn't the pcm read 5 volts on the signal pin with the key on
Customer: replied 2 months ago.
5.7 cross the pins.. 9.67 41 to ground
Expert:  Kenny Z. replied 2 months ago.

So 5.7 ohms across 41 and 58. See the attached chart. What does that tell you with 5.7 ohms across those pins. Chart is in Kohms

Expert:  Kenny Z. replied 2 months ago.

vref voltage potential will show zero if voltage is being consumed directly to ground.

Customer: replied 2 months ago.
Not really getting anything from 41 to ground. . Sorry.. does it tell me I'm losing my ground before it gets there. I'm not sure
Expert:  Kenny Z. replied 2 months ago.

Pretty much you have replaced everything plus wiring. If you are confident the wiring is good, I will opt out and give other experts a shot at this.

Expert:  Daniel Wilson replied 2 months ago.

Hi my name is***** fault is likely a problem in the wiring harness somewhere after the parts you have already changed but these are the potential causes to throw that code. Let me know if any of these have not been confirmed as of yet.

Possible causes

Wrong thermostat

Engine overheated

Low engine coolant level

Faulty Cylinder Head Temperature (CHT) sensor

Cylinder Head Temperature (CHT) sensor harness is open or shorted

Cylinder Head Temperature (CHT) sensor circuit poor electrical connection

Expert:  Daniel Wilson replied 2 months ago.

Hi, Did you get this resolved?If so, Please take a moment to rate as that is how the site credits my time helping on the site or let me know if you need more help and I will be glad to help further. 5 star and bonuses are always greatly appreciated.