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Old 04-22-2004, 08:03 AM
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Unhappy 90 Camaro RS Electrical Problem

My injectors are not getting a pulse. I have installed a PASSKEY bypass module, this wan't the problem. I have replaced the ECM, nope, either. Changed the Ignition Module on the distributor. Nothing yet. What is my problem.

My SERVICE ENGINE SOON light never goes on. I am starting here. The diagnostic charts are telling me that I have an open ground. I have a test light, vol meter, how do I test for an open ground. I have printed all the electrical diagrams for my car, but have no idea on how to test for an open ground.

Please, someone, help me!!!

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Old 04-22-2004, 01:35 PM
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Testing for Short to Ground

Notice
Do not insert test equipment probes into any connector or fuse block terminal. The diameter of the test probes will deform most terminals. A deformed terminal can cause a poor connection, which can result in system failures. Always use the J 35616-B Connector Test Adapter Kit or the J 42675 Flat Wire Probe Adapter Kit in order to frontprobe terminals. Do not use paper clips or other substitutes as they can damage terminals and cause incorrect measurements.


The following procedures test for a short to ground in a circuit.

With a DMM
Remove the power feed (i.e. fuse, control module) from the suspect circuit.
Disconnect the load.
Set the rotary dial of the DMM to the ohms position.
Connect 1 lead of the DMM to 1 end of the circuit to be tested.
Connect the other lead of the DMM to a good ground.
If the DMM does NOT display infinite resistance (OL), there is a short to ground in the circuit.
With a Test Lamp
Remove the power feed (i.e. fuse, control module) from the suspect circuit.
Disconnect the load.
Connect 1 lead of the test lamp to battery positive voltage.
Connect the other lead of the test lamp to 1 end of the circuit to be tested.
If the test lamp illuminates, there is a short to ground in the circuit.
Fuse Powering Several Loads
Review the system schematic and locate the fuse that is open.
Open the first connector or switch leading from the fuse to each load.
Connect a DMM across the fuse terminals (be sure that the fuse is powered).
When the DMM displays voltage the short is in the wiring leading to the first connector or switch.
If the DMM does not display voltage refer to the next step.
Close each connector or switch until the DMM displays voltage in order to find which circuit is shorted.
I hope that this helps..


let me know if you need any more info..
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Old 04-23-2004, 07:34 AM
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Thumbs up Testing 4 Open Grounds

Thank you so very much ... like seeing the light at the end of the tunnel, I understand now. If you disconnect a circuit (specifically, give it an open ground), the continuity should be infinite. If it is not, the circuit being tested is taking a shortcut to ground by other means!

Armed with this new information (I am new at this), I was able to test the fuel injectors, the ECM, and the EST. These are my new findings:

1) The EMC is getting a + reference signal from the distributor module (EST).

2) Both injectors are getting 12 volts when key is in the ON position.

3) PASSKEY Module is sending a 2.5-volt signal to the ECM.

4) This is the BIG ONE ... The ECM is sending ground signals to the injectors, but these signals are so weak that it's not enough to light even the injectors test light special tool. It does light up a regular test light, but that's because it is so sensitive.

Wrong Solution
-------------------
If I give the injectors a good ground -- jump them right to the battery negative, they open up like crazy and the injector test light, when connected, lights up my hole neighborhood. So I thought to install a relay by the injectors to receive the weak ECM ground signal and have it active a good solid ground from the battery and send it to the injectors. I was thinking of making the relay work like a transformer, an amplifier, if you will, for the ground. Then I realized that the ECM is sending a weak signal because something is wrong. It's not that the ECM sends a solid ground and it gets lost somewhere by the time it gets to the injectors. THE ECM IS SENDING A WEAK GROUND, to begin with.

Right Solution
------------------
It is obvious that the ECM is not receiving good signals from one of the sensors. I am sure of this because I found underneath my car a broken connector piece. Something is disconnected and that's why the ECM sends a weak ground signal. According to the ECM, conditions with this open connector do not call for a strong ground signal to the injectors.

Where do I begin? How many sensors are involved in the ignition process? Please, recommend me a plan of action.

Sincerely,

Julian Serna
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Old 04-23-2004, 07:52 AM
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Are you refering to a noid light? If the ecm is getting a signal from the module, your dist is good, the ecm does grd the injector at varying lengths called pulse width, depending on various inputs, the injector noid lights should pulse rapidly when cranking, maybe your injectors are defective, direct grounding for testing is not a good idea! Check all the ecm grounds and engine grds
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Old 04-23-2004, 09:54 AM
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Angry Ground Testing

Yes, I was refering to a noid light.

Status:
I am testing the ECM to ensured it has all good grounds.

Question:
It's there a relation between EST ground being sent from the distributor to the ECM and the ground being sent from the ECM to the injectors (the pulse width)? In other words, is the EST ground the source of the ground being sent to the injectors by the ECM?
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Old 04-23-2004, 10:33 AM
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No,The ECM only grounds the injector circuit directly, but, be sure to check all grounds as they are all common use! The module doesn't send a grd signal. if the noid doesn't flash and you have a reference from the module and good grounds, sounds like ecm fault!
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Old 04-26-2004, 05:35 AM
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Low signal

Hi,

Docvette here,

Had a simular Problem on a V6 chevy van....(at least it sounds simular) If it ran at all , it would last 1 to 5 minutes then not start for 2 to 3 days If then.

I did all the checks as outlined here with very much the same results.

FIRST may I add, do not try to "ADD" ground or POWER to the injectors...This can burn them up! They relay on a (as I remember) negitive pulse to operate supplied from the ECM. The little coils inside aren't built for high amperage.The B+ is (should be Static) and if I remember correctly, the pulse is 3 to 5 volts ??

After several parts, and shop advice, ton's of newly purchased diagnostic equipment, and 3 weeks of shear agnoy, I found the culprit to be a partially shorted injector, Which (when and if it would start ) Change value with heat, the warmer the engine the more it would short to ground. go out and stay out. and may or may not a few days later. run for 1 to 5 minutes...and so it goes...

I got Ohmic values for the coil on the injectors supplied by the local parts guy who dragged one out and measured it, and tested mine to find that my right injector was near short.$73.00 later I was upwardly mobile again. In thinking about it later I wondered why it wouldn't run on the one injector?? at least a little bit.??
I was told, and it seemed plausable, that because the one injector was bad it posed a load on Both injector B+ inputs which are common to each other. I was fat , dumb, and happy, so at that point, I really didn't care.

The problem never re ~occured again. ... So maybe another place to check?? ...Oh goody.....

Hope this helps a little
Doc
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Old 05-19-2004, 08:21 AM
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Talking Solution

Thank you all for your help. It turns out that the problem was a bad VATS module. This is the module for the security system. The systems involved are the ignition cylinder, the VATS module and the ECM. Well, rather than replacing the ignition cylinder or the VATS sytem, I hoot up with www.tbichips.com. They burn me an EPROM chip for $50.00 that totally bypasses the VATS system and that got my car started. Only problems was giving the starter relay a constant ground which I did.
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Old 05-19-2004, 02:32 PM
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Solution!

Juilian,

Doc Here:

Glad To here you have Resolved The Problem! Fine Job!

What Was it Bell Labs Said in the Late Forties....??
Computers Were on the Horizon..
.And They Were Going to make Life Sooo Much Easier and Faster For The Bi~pedal Multi~celled Species... THEY:

Never Stood in a line at Albertsons with 12 people in front of him, 2 quarts of melting ice cream , 3 Screaming Kids, and a Code Scanner That malfunctions 1 out of 3 times...

OR lost his pay check in the ATM deposit door....

Was Able to WATCH his luggage go to the Pyrenees Islands on a Computer Screen... at his destination Airport.... Tokyo Japan...

Relied on A computer Generated Voice To tell him 5 minutes after sitting on the side of the road stalled...."WARNING...LOW FUEL" ...HAH! lot you know...you don't even know the difference between a "DOOR" and a "JAR".....

Computers....Can't live with them...... Well, enough on that subject....

Glad to Hear you are Back on the Road!

Doc


===========
Yes, your bathtub is more
dangerous than flying,
but it's rare to be killed
by shredding aluminum and
burning aviation fuel in there.
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