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Ivan, ASE Certified Master Technican
Category: Cadillac
Satisfied Customers: 4871
Experience:  ASE Master Tech w/ 20+ years in the field. Self employed for 9 years. Member of AUTOLAB radio show.
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Cadillac Deville: 2003 Cadillac deville no start...Power in

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2003 Cadillac deville no start...Power in fuse box underhood with ignition switch off, but with switch on no fire

Hello and good evening. Are you still in need of assistance?

Your JA Expert,


Customer: replied 3 years ago.

Hello and good morning.


Yes, I still need help


Also, sound like the fuel pump is running while ignition switch is on non stop

Customer: replied 3 years ago.
Relist: Other.
no answer
Ok, I would like to start with something simple. With a voltmeter, let me know the voltage of the battery at the terminals, then at the battery bolts themselves that connect to the battery. Then try to see what is at in the cable itself. I am looking first for high resistance. On the battery cable side, see what that voltage shows when you turn the key to start. Let me know what you find.
Customer: replied 3 years ago.

Good morning


The car is at the customer house

Tested at their house yesterday with test light

She was driving the car and then the dash light started blinking, so she turn around and park the car

Voltage is at the fuse box until the key is turn on then no voltage on battery cable at fuse box and on max fuses

Then look real closely at the battery and the battery connections. Your problem has to be there. Look for corrosion where the battery bolt goes into the battery cable. Look also to see if the battery voltage drops also when the key is turned on. I truly feel the issue is going to be in that area.
Customer: replied 3 years ago.

I'm going to check the car, will be back online in an hour

Ok great, I'll look for your post.
Customer: replied 3 years ago.

Back online


Battery was dead, but the same problem

-fuel pump runs no stop

-no start , no sound clicking or nothing

-headlights stays on

-trunk and gas door don't work

-95% of fuses in fuse box underhood and under back seat with power with ignition switch in off position

problem a dealer job

Have you addressed the battery yet?

Customer: replied 3 years ago.

check voltage and replace battery

now voltage does not drop when switch is on

fuel pump runs with no key in switch had to disconnect battery

sounds like something is melted together, holding the fire

Ok, can you unplug the fuel pump relay and get voltage readings on each terminal of the socket? Let's find out why the pump is staying on. Let me know if you need locations

Customer: replied 3 years ago.

only check voltage only on one side, even change relay.and the dash stays on sometimes without key

Does the fuel pump shut off when remove the fuel pump relay?
Customer: replied 3 years ago.


Then the PCM is keep the relay grounded. Can you get codes via a scan tool out of this car? Body control module codes? Instrument panel codes?
Customer: replied 3 years ago.


nothing scans

operator error

Then I feel you have a PCM that has failed. It is keeping the fuel pump grounded. Unplug it and see if the fuel pump turns off. I am going to send you pinouts for the PCM. Make sure all powers and grounds are OK and present. I have to step out for a little while, but tell me what you found when you check these points at the PCM


Ivan and 3 other Cadillac Specialists are ready to help you