Ok guys so this is how the story goes...

My uncle bought a 1997 Bravada w/ a blown engine. He also had another 1997 Bravada as a daily driver. The Bravada w/ the blown engine is in better shape and has less miles on it, so he wanted the the good engine put in the Bravada with the better body. I told him I didnt have time to do it (I realized that was the first mistake I made) so he had some one else put it in then they couldn't get it to run. So now its back in my hands to clean up someone else's screw ups.


It has fuel but no spark.
The guy that put the engine in thought he had to change the steering column because thats what someone told him, do he did. Supposedly he changed it back after he found out that he didn't need to change it.

I picked it up and the distributor cap was zip tied down because he broke the distributor by over tightening the distributor cap. I lined up the 2 timing marks on the balancer to the indicators on the timing cover and the distributor was also out 180 degrees (which by this point i was not surprised).

I set the timing and dropped the new distributor in then i realized i had no spark. I tested the coil and it ohm'd the same as a new one(actually looks like a new one, so it could have been replaced also by the other guy).

The ICM tested good (took it to the parts store and had tested).
CKP Sensor is supposed to be new because the guy that changed the engine broke it (looks brand new).

The CKP Sensor has power of 8.5v and ground. I still need to check and see if it is putting out 5v signal to the PCM or not. That will be done tomorrow.

The ICM has 10v on term A and ground is good on term C. No signal from term D on the ICM to term C on the coil.( I checked the the wire and its good.

The coil also has 10v to it on term A but is not putting current to the coil wire. I checked the to make sure its grounded good to the engine and it is.

So here's what i still need to do:

Check for 5v signal from CKP to PCM (purple wire)
Check For signal from PCM to ICM (white wire)

8.5v to the CKP seems odd because it should have the same voltage as the ICM and coil.

Just thought I would post it up here to see if anyone has any other ideas.

Sorry the thread is so long just trying to be as detailed as possible.

Thanks in advance!

 

The Passlock security system needs to recognize the key that came in the vehicle originally. Swapping the column will cause the BCM and PCM to disable the injectors. It will NOT disable the ignition though.

Pink wire at the ignition module, and at the ignition coil, must show battery voltage with the ignition in the RUN position. Seperate circuits so check both of them.

White with black tracer wire and the solid white wire at the ignition module, and at the ignition coil, must show pulsing ground while cranking. To test for it, connect the ground lead of a test light to battery positive, and probe each wire with the test light probe while cranking. Test light should blink. This will test the PCM output to the module, and the module to the coil signals. If there is no pulse on the solid white wire at the ignition module, there will be no pulse on any of the wires at the module OR coil. This is the main pulse signal from the PCM that triggers the module, which in turn fires the coil.

 

Yea, column supposed to have been changed back on it.. I have to other PCM also.

I checked for the pulsing ground last night and it had none. I just went out to check if I had the 5 volt signal going to the PCM from the CKP sensor Via the purple wire and I did not have the 5 volt signal as I turned the crank by hand.

I also checked for signal from the PCM to ICM via the white wire on the ICM and i saw no change as I turned the engine by hand. I checked the wires by back probing.

The CKP sensor is new but it looks like it may not be any good.

I also have no security light coming on.


UPDATE: I exchanged the CKP sensor because it was not putting out pulse. I then installed another new one. I still have no spark. So I decided to swap the PCM out for the spare from the other Bravada and still no spark.

Parts that are new:

Distributor (other guy broke it)
ICM (tested bad at Oreilly's)
Coil (other guy replaced it) old one has still good too.
CKP Sensor (other guy broke the old one). Then I exchanged it because it wasn't pulsing.

So I am pretty sure that all of the parts are good.

One thing I am wondering about is if the CKP sensor will pulse if it has less than 12 volts going to it. Does anyone know for sure if it will or not?
When I tested the power from the pink wire on the CKP sensor it was 8.52 volts. The pink wire on the ICM and Coil both had 10 volts on them.
I put a different battery in it because the other one I think had a dead cell. It had 12.3 volts but didn't have enough amps to crank without the battery charger hooked to it.


I will check the voltages again with the good battery then post it up.


Thanks for the help so far.

 

Several things here:

The crankshaft position sensor does not operate on reference voltage. The pink wire comes from ECM IGN fuse #10, (battery voltage with ignition switch in the START & RUN positions). If the fuse is blown, or the sensor does not get voltage, the PCM will not get the pulse, and no blinkey at the coil or module. When voltage is applied to the sensor it creates a magnetic field. As the tone ring on the crankshaft passes through the field, the field is interrupted and it sends a pulse to the PCM. You aren't going to be able to read anything at the sensor on the purple or yellow wires. Try checking for ground pulse on the white wire at the ignition module while cranking. That's where the PCM sends the pulse to the module.

The crank sensor is very sensitive, if it is moved, removed, replaced, or disturbed in any way, the crankshaft position sensor relearn MUST be done, (requires a scanner capable of initiating the relearn). The engine will start & run without doing the relearn, but injector & ignition timing will be incorrect.

You need to keep the original PCM with the vehicle, don't use the one from the donor vehicle.

EDIT: If battery voltage is low, voltage on the pink wire at the crank sensor will also be low, possibly lower. Bunch of wire from the battery to the sensor, so the potential for voltage drop at the sensor is definitely there. Voltage Drop Testing

 

Thanks Captain,

I didn't realize that the crank sensor didn't use reference voltage on it. I am aware of the ECM IGN #10 fuse and it is good. I'll change the PCM back to the one I took out. I honestly am not sure which one was the original because the bolts were loose on the mounting bracket like someone had it out once already.
With a good battery the voltages read as:

CKP (pink wire) 11.62 volts
ICM (pink wire) 11.62 volts
Coil (pink wire) 11.62 volts
Battery 11.93 volts

These were all with the key in the run position.
With the key off the battery voltage is 12.7 volts.
I decided to take the CKP sensor out to see if it was magnetizing and it is. If I touch the end of it with a wrench the fuel pump kicks on but no spark signal. If I turn the crankshaft by hand with the sensor in, the fuel pump does not kick on when the tone ring passes by. I put my magnet up in the hole when I had the sensor out and it seemed like it was in there still. I felt with my finger when it was out also and it felt like it was in there also.

The timing cover looks really clean like it may have been off before the other guy put the engine in it plus the bolts have fresh rust spots on the heads like a wrench has been on them.

I did not have a pulsing ground on the white wire on the Ignition Control Module when I checked it. I put the one end of my test light on the white wire and the other end on the positive on the battery and cranked it and there was no ground pulse.


Thanks for the help so far I appreciate it.

 

Certainly sounds like the CKP is working. If the engine has been apart, and they didn't put the tone ring back on the crank,






or put it on backwards, (if that's even possible) the CKP will obviously not send a pulse.

Another possibility is that the PCM is not receiving the pulse.

First test makes sure the sensor is getting voltage and ground. From your previous test, it probably is, but check it anyway. Disconnect the CKP connector. Ignition in the RUN position. Check voltage from the purple wire to the pink wire. Must be battery voltage. NOTE: The purple wire is NOT the same as vehicle ground, so it must be tested at the connector.

Next test is the yellow signal wire from the CKP to the PCM. Ignition OFF. Unplug the blue connector at the PCM, and the CKP electrical connector. Check resistance on the yellow wire from the PCM connector pin #31 to the CKP connector. Must be less than 5 ohms.

You can test the signal on the yellow wire when cranking, but it requires a DVOM with the capability to test "duty cycle". Don't attempt it without the proper equipment.

This shows the CKP circuit:



Make sure all fuses, in both fuse panels, show battery voltage on both terminals of each fuse:




Next step: Post your results.

 

Ok I will go check a few things and post my results. The diagram I have must be wrong because it shows the Yellow wire as ground from the PCM and the purple wire as the signal on the CKP.

Here is the diagram I have if I posted it right.

The first link doesnt work. I tried to remove it.

 

Second link doesn't work either. The schematic in post #6 is right out of the GM service manual. Let me guess, your link is from a Haynes or Chilton manual. Both are a joke, unless you need to learn how to change the oil & filter. Half of their information is incorrect, the other half is missing. They leave it up to you to figure out which is which Invest in a GM service manual. 3 volumes, over 3K pages, one year, one model, almost 6" thick, compared to Haynes & Chilton 150 pages covering 10 years. Ebay sometimes has decent used ones around $150.

 

Lol, stupid link.

Well anyway I checked the voltage, pink and purple create battery voltage.

The yellow wire has .7 ohms and the purple has .6 ohms.

 

See if it posted this time.

Edit: I actually found this one online when i was trying to find a diagram and searching on Google about my problem. The haynes doesn't even have it in there.