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Dave Nova
Dave Nova, Cadillac Technician
Category: Cadillac
Satisfied Customers: 1522
Experience:  ASE Master Certification. GM World Class Certification
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I have a 99 deville (4.6) with no injector pulse do you have

Customer Question

I have a 99 deville (4.6) with no injector pulse do you have a flow chart? I have spark and I have tested the security and ICM.
Submitted: 1 year ago.
Category: Cadillac
Expert:  camerontech replied 1 year ago.

hi there,

im cam.

This sounds like a ground issue that i have seen before. the pcm has an injector driver that has its own ground, i am going to send you the wiring diagrams for the pcm (the ones with the grounds in it), check the pcm grounds at their bolt points and i would definatly also check at the pcm as well.

Expert:  camerontech replied 1 year ago.

3 and 4

have look here before you go any further

Customer: replied 1 year ago.
Cameron, I'm having trouble viewing the attached diag on my I-pad. They load and open for a split second then go to a black screen.
I will attempt to open them on my laptop in the morning as it is 11:40 p.m. here now. If not, I have access to prodemand wiring diagrams and I can try to locate them if you want to designate pin locations if I can't get yours to open in the morning.
I hope you are correct on the simple ground fix. This one has me stumped.
Expert:  camerontech replied 1 year ago.


your laptop should be able to open them no problem, i donk think ive had any issues with them before.

if not, its good that you have prodemand..

just pull up the ecm wiring diagrams and locate the grounds and make sure they are good. this was the problem i had before. the pcm ones are located on the rear right of the engine, but the nice thing is grounds are easy to make new ones instead of chase them lol.

at the rear of the engine too, there should be a round harness connector too, make sure those pins are good there too.

let me know and good luck!


Customer: replied 1 year ago.
I just tested all grounds (black/white wires) at the PCM and they are all good. I also failed to mention that I do have a constant (with key on or cranking) power going to my injectors and I get a single flash of the noid when it first begins to crank so I know the injectors are just missing the PCM ground control. I have read this pulse is used to aid in starting until the PCM receives signal from crank and cam sensors. I have also replaced the cam sensor. Not a fun job on the Northstar.
Customer: replied 1 year ago.
FYI I also have constant spark while cranking. I'm sure it would run on starting fluid.Dan
Expert:  camerontech replied 1 year ago.

Hi dan

thanks for the detailed info.

I thought about that I forgot to ask if there was 12v at injectors too, but you have eliminated that.

Can you make sure that the throttle position sensor is not full 5 volts at this will shut down the injectors too.

Have a look at that and eliminate that.

I am at work. So I'm going to check a few things and get back to you when I get home.



Customer: replied 1 year ago.
I had previously eliminated the clear flood mode as well. the TPS has normal values. (Under a volt at closed throttle and 4 something at WOT). Also I wanted to mention that I didn't locate the actual ground at the rear of the block (no lift at home) and it's outside, but I assume it's there due to the PCM ground verifications. I also had read to disconnect the MAP and try to crank it and it didn't help. The MAP also has normal values. I did attempt to scope the crank sensors (it has two) and both had similar patterns. I'm fairly certain I disconnected them one at a time and it killed spark? Not positive on that. I also see an RPM on the scanner while cranking but it does take a few revolutions. Good Luck friend. P.S. I'm an ASE Master cert tech as we'll and this one has me puzzled. It's also been at three other shops in town before they dropped it to me so many hands have messed with it :(
Expert:  camerontech replied 1 year ago.

hi there,

still trying to figure this out. thanks for the patience

thanks for all of the info though, you have hit everything i would have so this is a tough one. im tryign a few things to see what i can come up with.

Expert:  camerontech replied 1 year ago.

this waste spark system is wonkey on these,

the cam and crank go through the icm first (which is why you have spark), than the icm sends signal to pcm to the injector drivers.

did you try a new icm?

if not i probably would, if not...

the i think its wiring between the icm and the pcm, the signal is prbably there but weak to a possible chaffed wire.

so each wire will have to be continutiy checked from icm to pcm, i think this is where our problem is

I have included a link for you on a really good desccription and article on caddillacs wonderfull ,lol, system.

Expert:  camerontech replied 1 year ago.


you did a key relearn procedure too?


Customer: replied 1 year ago.
Hey Cameron,I haven't done the key relearn yet? Not sure of that procedure but I can try to look it up.
Yes, I do several Cadillacs and I switched it with a 97 Deville that I own myself and it ran fine.
I'll check out the site above now.
Expert:  camerontech replied 1 year ago.

im pretty sure you just leave the key on fir 20 mins, lol.

the theft can cut the injector drivers too, thats why its good to do a relearn.

if that doesnt work,

we will have to check every wire from icm to pcm

its nice to talk to another tech, and i enjoy some of these nightmares, hopefully i can help you find it because i can tell you know your stuff


Customer: replied 1 year ago.
I "thought" I knew my stuff lol. It's funny I had already printed off the entire article you suggested and it's on my workbench :) I found it a week or so ago and thought it would also be good info for ign mods on future projects. I will look into the ICM to PCM wiring soon. As stated the car is outside and we are now getting rain and will be for a couple of days here but if it lets up I will tackle it again. I too enjoy a challenge. My shop is always the one that gets these kind of cars. I'm also the only shop for miles that does imports (Jag, BMW, MG, etc). I take it you don't have a GM flow chart for no inj pulse on this old machine?
Expert:  camerontech replied 1 year ago.

that the first thing i looked for,

Almost every chart i looked at said replace the pcm , lol.

that article is a great article,

im like you, im a well known diagnostic tech, the worst part for me is who do i call when i need help lol.

ill keep this open and if anything comes to mind ill let you know too.

I remember something a long while back about wiring in the harness around the intake, do you think i can pull those cobwebbs out??? nope.

let me know what you find and good luck!


Customer: replied 1 year ago.
This is what I found for the relearn, but I'm not getting any security codes or dash warnings but I'll check it out.
I did verify that I get 5volt at the security wire at the PCM and it drops to 2.5 with the resisted key in the cylinder as it should.Turn ON the ignition, with the engine OFF.
Attempt to start the engine, then release the key to ON (vehicle will not start).
Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF.
Turn OFF the ignition, and wait 5 seconds.
Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes (the vehicle is now ready to relearn the password ***** the next ignition switch transition from OFF to CRANK).
Important: The vehicle learns the password ***** the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.Start the engine (the vehicle has now learned the password).
Customer: replied 1 year ago.
Ok I'll check back in when I have more testing info