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Ask Dave Nova Your Own Question
Dave Nova
Dave Nova, Cadillac Technician
Category: Cadillac
Satisfied Customers: 1522
Experience:  ASE Master Certification. GM World Class Certification
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Cadillac Escalade: I have a 02 escalade that will run with

Customer Question

I have a 02 escalade that will run with the TAC unplugged but will die if you plug it back in
the fuel pump relay starts clicking really rapid to
Submitted: 1 year ago.
Category: Cadillac
Expert:  Gm Tech (Cam) replied 1 year ago.
Hi there, I am Cam. Does the fuel pump relay click rapidly only when the TAC is plugged in?
Customer: replied 1 year ago.
yes
Customer: replied 1 year ago.
if I unplug it the engine will start and run just no throttle response
Customer: replied 1 year ago.
you there
Expert:  Gm Tech (Cam) replied 1 year ago.
Yes I am, sorry, there is issues with eh website.
Expert:  Gm Tech (Cam) replied 1 year ago.
So this sounds like a ground issue. Have you done any recent repairs to your vehicle?
Customer: replied 1 year ago.
no
Expert:  Gm Tech (Cam) replied 1 year ago.
Ok, lets check the grounds. On the back of the intake on the passengers side is a ground wire, G103, lets check that one, check the one on tieback of the drivers side cylinder head which is g104, then lets check the ground wires under the drivers door on the frame. In all cases pull on the wiring to see if the wire gives. IF not then take them off and clean them to bare metal.
Customer: replied 1 year ago.
do you have a wiring diagram to go by?
Expert:  Gm Tech (Cam) replied 1 year ago.
here is the engine one.
Customer: replied 1 year ago.
I checked all the grounds to the battery negative post they are good
Customer: replied 1 year ago.
I have tried a different TAC module. the same thing
Expert:  Gm Tech (Cam) replied 1 year ago.
These grounds are to the engine block and the frame, not the battery.
Customer: replied 1 year ago.
I hooked the negative end of my DVM to the grond on the battery and OHMed them out
Expert:  Gm Tech (Cam) replied 1 year ago.
I can understand how that can be viewed as a good test, but ohms can be misleading. My experience has been that a physical inspection as I outlined is the only way to truly eliminate these grounds.
Customer: replied 1 year ago.
ok im checking them now
Expert:  Gm Tech (Cam) replied 1 year ago.
Perfect. I cannot stress enough to use a wire brush or something to clean the surfaces to bare metal.
Customer: replied 1 year ago.
cleaned them and tightened them good. still same thing
Expert:  Gm Tech (Cam) replied 1 year ago.
OK, is there signs of corrosion, rodents or wiring issues under the underhood fuse block?
Customer: replied 1 year ago.
no the plug was dry
Customer: replied 1 year ago.
I checked the fuel pump signal wire from the ECM to the relay it has 11.9 Volts all the time with the switch on. its only suppose the have it for 2 seconds right?
Expert:  Gm Tech (Cam) replied 1 year ago.
When the key is first turned on, that is correct, 2 seconds. So if that stays at battery voltage then we may have an issue with the wiring or PCM, hold on for a moment to see if I can find a common link between the 2 that than the PCM.
Customer: replied 1 year ago.
ok
Expert:  Gm Tech (Cam) replied 1 year ago.
Ok, so other than the Powertrain Control Module (PCM), these do share the IGN 1 relay. that may have failing contacts. Lets ttry seating that for another relay with the same numbers stamped on the top.
Customer: replied 1 year ago.
already swapped relays still the same
Expert:  Gm Tech (Cam) replied 1 year ago.
Did you check under the fuse block for rodents and such? If no then we may be looking at a failing PCM. IF you tap sharply on the housing, does it change anything?
Customer: replied 1 year ago.
no droppings or and signs of rodents the wiring looks good. I will try the tappin g hold on a sec
Customer: replied 1 year ago.
same thing still
Expert:  Gm Tech (Cam) replied 1 year ago.
Pop the tilt lever out and take the lower trim of the column off. With your multimeter set to DC volts, place the red lead on the red wire. With the switch turned on, test the other leads with the black wire. Record the reading and let me know what those are. Repeat the test on the red/white wire. Let me know the results.
Customer: replied 1 year ago.
is this for the security? the reson I ask is about 2 years ago I lost my key and I had a cheap key make then the security has been turned off for 2 years.
Expert:  Gm Tech (Cam) replied 1 year ago.
No, there is no chip in the key, these use a sensor in the key cylinder that measure the rotation. I am thinking a weak contact on the ignition circuit itself.
Customer: replied 1 year ago.
ok ill check
Expert:  Gm Tech (Cam) replied 1 year ago.
ok