Five Volt reference voltage circuit C low no starting issue

FUSIONTDCI2007

MEMBER
2007 FORD FUSION
1.4L
4 CYL
TURBO
MANUAL
50,000 MILES

I have a TDCI. The car has a five volt reference voltage issue. The engine code showed a low circuit C voltage issue. As a result of this the car does not start. I have used a voltage meter and checked all the reference sensors and all of them were fine. I have been told it could be the EGR valve as well, so I tried to unplug that to see if it works. The car did eventually start after a while, but after ten minutes cut off. The voltage decreased to 0.25 and did not start anymore. I have been told that without the EGR the engine should run fine, but that is not the case now.

What could this be and how do I fix this? Any help is appreciated.

4 Replies

KEN L

MASTER CERTIFIED MECHANIC
42,895 POSTS

It sounds like you have an 02 sensor or injector that is shorted causing the the voltage drop. Please disconnect each sensor until the voltage returns.

Can you give me the code number please?

Cheers, Ken

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Friday, October 6th, 2017 AT 9:27 AM

FUSIONTDCI2007

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3 POSTS

Hi there Ken,

Thank you for your response. The fault code is P0698. I checked all the sensors but it didn't make a difference.

Thanks.

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Friday, October 6th, 2017 AT 2:07 PM

FUSIONTDCI2007

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3 POSTS

I have to note as well that when the car does start, it runs very smoothly and doesn't show any issues at all. I checked both the O2 sensor and injector as well

Thanks

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Friday, October 6th, 2017 AT 2:10 PM

KEN L

MASTER CERTIFIED MECHANIC
42,895 POSTS

Hum bad sign. It sounds like the transformer inside the PCM has gone bad or you have an open circuit in one of the harness wires. I was hoping a sensor was causing it and that there were more codes.

Here is a guide and some diagrams to help us run some tests before commending the PCM.

https://www.2carpros.com/articles/how-to-check-wiring

Please let us know what you find.

Cheers, Ken

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