Neutral Safety Switch Code and no start on 4.9L. (Page 1/2)
Dennis LaGrua SEP 30, 04:47 PM
I have been trying for months to start my 93 Cadillac swap to no avail. It once ran ok but will not start again. We have fuel pressure but no injector pulses and no spark. New distributor put in. After checking for battery power, ign+ and all grounds at the ECM they all check out. The scan tool says "neutral safety switch" but the starter engages and turns over. In doing further research I find that another lead from the neutral safety/trans selector switch goes to the ECM as "trans input P" I would like to test this input but unsure if it supposed to be a ground or a 12V input. I believe that without a ground or some signal to pin A2 the ECM won't turn on. Can anyone suggest a solution?

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

olejoedad SEP 30, 06:25 PM
It's a ground.
Dennis LaGrua OCT 01, 04:40 PM
Thanks Joe. Will test first but if N/C I'll hook ECM pin A2 to ground and see if that does it. Come to think of it I did change the Neutral safety/ trans range switch before this problem surfaced. It is indexed properly but it could be a loose connection or a bad switch. Scan tool still says "neutral Safety switch" so that may be it.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

phonedawgz OCT 02, 12:03 AM
During cranking (under 400 rpm) the PCM/ECM does not control spark. The problem isn't going to be PCM based.

You have power going to the dist, I assume, why don't you have spark?
Mickey_Moose OCT 02, 07:31 AM
What phonedawgz said ^^^
But it could be more along the lines that the ECM is not getting the distributor reference signals. Maybe a bad ECM? I assume you have power at the injectors?


But, as per your specific question: technically A2 is "not needed".

IIRC the transmission inputs are a binary code for what gear is selected. That being said, I think the symptom when C10 and F7 are not connected, the car would stall when coming to a stop (or something along that line). So in theory it should start with none of the connections made. This would be simple to check by disconnecting from the transmission and just grounding C10 and F7 and leaving the others disconnected.


quote


Standard transaxle:
You must connect ECM C10 & F7 to ground, the other transmission pins can be removed.






quote


Highlighted areas are 'must use' connections (in most cases):

NOTE: it was pointed out by ImperfectTruth that A7 is not highlighted and YES this is needed












https://www.fiero.nl/cgi-bi...My+4.9+wiring+thread

[This message has been edited by Mickey_Moose (edited 10-02-2023).]

Dennis LaGrua OCT 04, 07:26 PM

quote
Originally posted by phonedawgz:

During cranking (under 400 rpm) the PCM/ECM does not control spark. The problem isn't going to be PCM based.

You have power going to the dist, I assume, why don't you have spark?


Yes power is going to the distributor but no spark. Still don't know why I get the neutral safety switch code. Will check all fuses this week. This no start problem has had me stumped for quite a while.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Spadesluck OCT 11, 08:05 AM
I agree with Joe, sounds like a ground. Did you check the C10 and F7 pins to make sure they are grounded?
Mickey_Moose OCT 12, 05:16 PM
Dennis: What is the code (number) your are getting? Any other codes?

Auto or manual transmission?
lou_dias OCT 12, 06:35 PM
OT:

Is pin B-12 actually 2000ppm instead of 4000ppm for the odometer?
I'm looking to convert it to analog so my speedo becomes usable after switching to the F40.

[This message has been edited by lou_dias (edited 10-12-2023).]

Mickey_Moose OCT 13, 01:55 PM

quote
Originally posted by lou_dias:

OT:

Is pin B-12 actually 2000ppm instead of 4000ppm for the odometer?
I'm looking to convert it to analog so my speedo becomes usable after switching to the F40.




I seem to recall that it was - but that was a long time ago for me to be certain. But in the back of my mind I seem to think I did check that as I was going to use it for something.