Dadgum Tach Signal

I'm putting a cs324-T and IPP-ME in my 2000 Silverado 4.8L and I keep getting a flash code that says  Over-crank Protection indicating that I am not getting a Tach Signal.  I am connected to the White wire at Pin 10 of the Red connector on the ECM and my DMM detects 6.8vac.  When I rev the engine, however, I don't notice any change in the reading.  Isn't it supposed to change with the RPM's?

Is there any other place I can pick up the Tach Signal?  I tried a wire at one of the injectors but got the same results.  Is that signal found at the tachometer and available under the dash perhaps?

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abbloom -- just an average handyman struggling through today's high technology.

ECM is located near the battery, down low, between the fender and the fan under the black plastic cover. On the 4.3L, the tach wire is at pin 20 in the connector labeled 'red', and VSS wire is at pin 3 in the connector labeled 'black'. On the 4.8L, 5.3L, and 6.0L, the tach wire is located at pin 10 in the 'red' connector, and VSS wire is located in pin 50 of the 'red' connector.

Make sure that you are getting the correct tach learning flash back confirmation from the CS324T unit. If you do not get this confirmation that the tach is learned, then the truck will not start. Do exactly as the instructions tell you and have the hood open so the PURPLE wire is grounded.

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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA

Have followed all those instructions to the letter.  Phooey!!

I think I'll need a little more info about that Tach Signal before I get this solved.  Is that signal supposed to rise and fall with RPM's?

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abbloom -- just an average handyman struggling through today's high technology.

Make sure that your dmm is set to read a/c voltage when checking for your tach signal. It should read between 1-6 volts.

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Sound Pressure

You know you have the right amount of pressure when your eyes start to water! Now you've got Juice!

you mentioned in a dififerent post that you were able to get the starter to crank but not start the car. It sounds like you must have learned the tach. I would try grabbing the unique wire at the injector again and follow those instructions to the letter again. Just last night I put a 324T in and had a tach wire that tested 1.3V AC and it didn't work. So I grabbed the injector wire which was close to 2.3V AC and it worked.

To answere you question from above: Yes the tach signal should increase with the RPM's.

Keep us posted

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J Rilla

Owner/Installer

I moved the Tach wire over to one on an injector and now the signal fluxuates with the RPM.  Hurrah!  However, the ac voltage seems awful low.  At idle it is less than one volt.  Should I look for another injector wire, or are they all the same?  (I hate to cut into every wire to test it.)

I am able to change the Tach Adjustment so the engine cranks longer, but it still does not start.  What about the Ignition 2 wire?  Is that what keeps the motor running after it fires?  If I unplug the modules and  plug them back in to start from scratch it seems like the motor actually starts for a fraction of a second on the first ttempt.  Could you explain how and why you use a relay and resistor with Ignition 2 ?   How can I tell if the IPP-ME learned the bypass properly?  Does it make a difference when and how I plug in the modules when I am using them together?

I feel like I'm really close here.  I'll keep trying until you give me another clue.

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abbloom -- just an average handyman struggling through today's high technology.

Sorry if that was unclear, I use a relay and a resistor to bypass the Passlock II anti-theft device, instead of using bypass modules like the IPP-ME, or others. I used to use them and now they are just a waste of time. When you use these modules, if the car doesn't start, you dont know if it is the tach, the passlock, ignition wire missing, your battery is dead, whatever the many possibilities are.....If you use the relay and get a trimpot to dial in the resistence or make a trip to Radioshack during the installation with your neighbors car, You are guaranteed that if the car does not start, that it is not the passlock. I know this may be your only passlock bypass you may ever do, but if you get fed up with this, I would seriously consider it as a way to relieve some of the trouble-shooting headache. Even if this isn't your problem, it will at least eliminate that as a possibility.

Were you able to learn the tach signal after grabbing the injector wire? I would let that be the judge of whether or not a tach signal of less than 1V AC is enough. Cheaper DMM will not give the best results. I still use a $25 Radioshack model that is not accurate but it is consistent, so i am able to work with it. I noticed that compared to my $300 Fluke, it produces consistently lower readouts.



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J Rilla

Owner/Installer

I'm getting pretty discouraged now.  I was finally able to talk to Trilogix tech support and the guy said to get the Tach Signal off the White wire behind the guage cluster.  It is supposed to be the cleanest signal there is.  So why am I now measuring like .10vac which revs to .2vac?  And nothing has changed...crank but no start !

He also said if the IPP-ME was the problem, I wouldn't be able to start it with a key.  He seemed more interested in getting me off the phone than answering my questions or solving the problem.  And now I can't even call back before Monday !

I may switch back to the Tach Signal at the ECM, but I'd like to try using a relay instead of the IPP-ME.  Let me see if I know how it's done:

• 85 to PINK - Ignition 1
• 86 to WHITE/ GREEN - Ground Output  when RS is running
• 87A to keyside of YELLOW Passlock
• 30 to other half of YELLOW Passlock
• 87 to TrimPot which is connected to ORANGE / BLACK Passlock

Will I need a 1amp diode on the Ground Output into the relay?

I wish someone with a 2000 Silverado like mine would jump in here and set me straight on all this, but I appreciate you hanging in there with me.

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abbloom -- just an average handyman struggling through today's high technology.

I have never had a good customer service call to any company they all should be fired!  Ok now that I said that;  I installed a different unit a couple of weeks ago on a 98 silverado, but that wire was different.  I did a 2001 last year and that sounds like the same wire, but that once again is on a different unit.  You said you could get the tach to change so it cranks longer, so I assume that means that you were able to learn the tach, right?  so keep the tach where it was when you had that and try the relay with a resistor like you have in your post above.  Let me know if you need to know how to measure the resistence. well nevermind it is easy since the yellow wire is already cut and the ORANGE / black is tapped.  connect the yellow wire again, then start the car with the key.  separate the yellow wire, and measure the resistence between the key side of the yellow wire and the ORANGE / black wire, then reverse the leads and use the higher of the two resistences.  The nice thing about a trimpot is that is is accurate no matter how cheap the DMM is as long as it is consistent.   I do not use the diode when I do the relay method (only before when I usewd the bypass modules), but maybe I should, I haven't had a problem yet.  It sure cant hurt (unless you put it the wrong way).

Keep me posted, You will get through this and then all the disappointment will come back because you wont ba able to have the car come pick you up at the door after it is remote started (like James Bond).

Dont be discouraged though, these are the easiest problems that you are dealing with.

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J Rilla

Owner/Installer

Okay, Okay, I'm going to play this thing the jrilla way.  I certainly have more faith in your experience than Mr. Help-Desk-With-A-Flowchart-In-Front-Of-Him-And-Hands-As-Soft-As-A-Baby's-Butt.  Since I removed the Starter Interrupt Relay when I figured out it was just an Anti-Grind Relay, I can use it for the bypass and I'll only have to pop for a trimpot.  I'll even splurge and buy a 1amp diode, what the heck. 

With the bypass relay in place and the Tach wire back at 6.8vac in the ECM, the stars and moon will surely align and all will be well and right in RS Land.  I just know it. 

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abbloom -- just an average handyman struggling through today's high technology.

keep me posted and let me know if you need any help with anything else

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J Rilla

Owner/Installer

WOOHOO!!  It works!  It works!

JRilla, YOU DA MAN!!  That is of course if J stands for John or Jack or Jerry and not Jasmine or Jill  ;-)

I ripped out the IPP-ME (why is there a market for these things?) and hooked up a relay with a 1amp diode going into the coil, measured the bypass resistance, adjusted the trimpot for 6.31kohms, and punched the button.  Well the first time, the motor cranked and it sounded like it started, but it kept on cranking and shut off after about 10 seconds.  Uh-oh, Overcrank Protection!

Then I remembered I needed to switch my Tach wire back from the tachometer to the ECM where I had it originally.  Punched the button again and it worked!  I still don't understand why the IPP-ME didn't work, but that's Trilogix's problem now.  I'll be returning it to them this week.

The cold weather this week will be a good test for the accuracy of the trimpot, but I'm confident it will be OK as I bought a 15-turn pot for more accurate tweaking.

Thanks again, JRilla!  Obviously, I couldn't have done it without your help.

And many thanks for the existence of this forum.  It's a great service to bumblers like me who need a helping hand from someone who really knows the answers!

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abbloom -- just an average handyman struggling through today's high technology.

The trick these days is to know when you need to rely on today's technological advances, and when to just do it the old fashioned way.  That's good to hear it went well.  If you are at all concerned with the trimpot, you can always buy a resistor within 5% of 6.31K Ohms, but make sure you put your test leads on the resistor to make sure that your DMM is accurate.  I buy stiff trimpots and secure them inside a box my relays come in.

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J Rilla

Owner/Installer

I'm not really concerned about the trimpot ; It's just that I read where big changes in temperature can affect the resistor value.  If it does, it will be nice to be able to adjust it. 

My installation won't be as pretty as yours, but I think most of the wires will bundle up OK and I'm going to try to superglue the trimpot to the relay.  I soldered the wires to the pins on the trimpot, then slid heatshrink over the joints.

I tried a remote start from way inside the concrete building where I work and everything happened the way it should.  Really pleased with the range.  Sure glad I got it to work in time for this cold snap that just hit us.  Only 10F this morning!  But roasty toasty in my truck. 

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abbloom -- just an average handyman struggling through today's high technology.