If crank sensor bad will it always give a code?

[HANK1948]

I was wondering If crank sensor is bad will it always give a code. Were having problems with my brothers 95 new 18:1 motor to relearn TDC offset. It wont relearn it seems to sometimes, very shortly then reverts back to the original spot. The truck runs and goes down the road alright but it starts very hard when warm and stalls a few times untill you get it going then it seems alright. The only code is the stepper motor code and that one Iam assuming thats because the timming is not right.

any suggestions? :confused:

[Kennedy]

It needs to miss 8 counts in a row to set a code, but you can simply watch it with a Tech tool and see what it misses.

If you have a stepper motor code you need to rotate the pump to allow the desired to track with actual. If you can't physically get there, then something is assembled incorrectly OR there is a key partially sheared.

[Slim shady]

Hey Hank

Your stepper motor code sets when the desired and actual timing don't match. If the stepper motor cannot correct the actual to match the desired and it is not the same by more than five deg plus or minus the code will set.

When we tried to do your TDC learn I did check to see if there were any crank ref or cam ref misses when running. There were none. (I am the one that has been helping him set his TDC offset, I have done a few, been ASE Master Cert for 20 years,doesn't mean I know anything, but I have done a few things in the 20 years making a living at the dealer.)

Initially when we first read the TDC offset it was -.97 and holding. We then adjusted the pump to get the motor to stay running and set the TDC learn. The first set produced -1.57, on the second try we got -1.41 then on the third try the TDC went to -2.02 and will not set at anything in between 0.00 and -2.20

When you called John K he gave you a procedure to rest the TDC learn to 0.00 by holding the accel pedal to the floor for 1 minute and this reset the TDC learn to 0.00. Any attempts after that have netted only -2.02 or 0.00 no matter where the pump is set. The pump has been at one extreme to the other and it will not set at anything other than 0.00 or -2.02.

I have asked around and been told that the after market power chip may not be reconized by the ECM / power train control module PCM. I don't know if anyone else has had a problem with an after market chip not being able to relearn TDC. Just a thought not a statement.

I suggest we try a factory chip and see if the PCM will do a relearn. Then we will be able to rule out the Power chip as a possible cause. If the TDC will relearn with the factory eprom then it may be a program glitch with the power chip or a sensitive PCM that doesn't like non factory chips.

Since you never had a TDC relearn performed when you replaced the factory eprom with your new power chip it may not have become apparent until now. I doubt may people do a TDC relearn when they replace the factory eprom with a new after market chip since they don't have the tools to do so.However the fact it set the first 2 times is interesting and perplexing.

Any other suggestions would be appreciated

Slim

[Kennedy]

Sounds like the pump needs to be rotated a bit to the passengers side and redo the learn. Keep going until you gt it back where it should be.

[HANK1948]

In reply to John: We have tried to move it back until it would learn the offset again as it did when we initially tried. But then as were moving it a "hair" at a time we end up past the point where we initially learned the offset at -0.97' then to the point where it wont start. For whatever reason we have not been able to have it learn anything other than -2.02' no matter the position of the IP. We were told that the ECM has locked this as a default (they stated 0.00' and -2.02' are default settings) because it was past the range of recognized offset. In order to "reset" the ECM that with the key position on to hold the throttle down for 1 minute, turn the key off, and the start the engine and learn the offset. We have tried this numerous times with no success (and yes it was with the IP in numerous different positions). As stated by Slim Shady we will attempt to learn the offset using the stock EPROM on Friday just to see if has anything to do with the reprogrammed EPROM.

John: Is this a function of the EPROM or ECM?

[Kennedy]

The eprom will not affect it. You likely only need to move the pump a hair.

Go into Time set mode (assuming the engine will stay running) and set the actual to about 3.5

[Slim shady]

John

We have already done that and the offset will still set at -2.02, or stay at 0.00 nothing else. We have disconnected the battery to kill the keep alive memory and the learned settings but nothing has helped.

Unless the PCM has more than one eprom (electronic read only memory)the other memory is ROM (Read only Memory) I don't see what else may be causing it. The cal pack is ROM memory,Or flash memory the pcm also has a capacitor/ battery to keep the learned memory intact in case of a short term power loss, seconds not minutes. Or maybe I don't understand, it may be something real simple I have overlooked, happened a few times before.

How about Ronnie Joe can we get him in on this I have read a few of his posts and he seems to have a good working knowledge of the IP and PCM.

Slim

[rjschoolcraft]

Is the "stepper motor code" that you referred to DTC34?

If so, the 95 GM manual says, "A damaged or misinstalled crank sensor may set a DTC 34." All the trouble that you are having makes me think that the PCM can't figure out where the crank is relative to the cam ring in the pump.

I suggest digging into the crank sensor further.

[Kennedy]

Are you using a Tech 2 or the pedal routine?

In order to learn:

ECT must be sufficient

No DTCs present

You can do it in minutes with a Tech 2. Hours manually...

[Turbine Doc]

Originally posted by kennedy:
Are you using a Tech 2 or the pedal routine?

In order to learn:

ECT must be sufficient

No DTCs present

You can do it in minutes with a Tech 2. Hours manually... Greater than 170F on ECT I like at least 180F because if it cools down during the time it takes to set it you won't know learn command isn't doing anything.

[Slim shady]

All right gentlemen

I have checked coolant temp 195 and I am using a Master Tech Scan tool that is able to do TDC relearn which I have done on no less than 8 vehicles, mine included.

Ronnie Joe the stepper motor code is DTC 34, (sorry for that)

The code is not hard right now or a history code and it only sets when the actual and measured are out by more than plus or minus 5 degree. If we set the TDC with the scan tool in the TDC set mode, we can get the actual and measured to be within 1 degree of each other. Then clear any History codes no current codes, try to set the TDC learn and it still will set -2.02.

The Cam and Crank reference do not show any missed pulses. I can check the Crank sensor with an oscilloscope to see what the wave from looks like. I doubt that the crank sensor is bad but I will check it.

It was odd that it learned three times then had this problem.

Slim

[Kennedy]

Originally posted by Slim shady:
All right gentlemen

If we set the TDC with the scan tool in the TDC set mode, we can get the actual and measured to be within 1 degree of each other. Then clear any History codes no current codes, try to set the TDC learn and it still will set -2.02.


Slim Can you do Time Set?

I'd like to see you do time set, adjust to 3.0 actual MOL, and then do TDC Learn. Then redo TDC learn again.

[Slim shady]

Yes I can do the Time set and have! Did that so I could keep the desired and measured within the 5 degree window. This way the DTC 34 (stepper motor code) would not set.

I put TDC instead of time set. MY mistake, can't work and post at the same time.

I can't think of anything I have forgot. Where are we going with this!

[Slim shady]

Already been done more times than I can count! If I could line up the distance it was adjusted you could make a line 2 feet long.

[Kennedy]

What part of MI is the truck in? Near Holland? Actual needs to be at 3.5 or less during Time Set which is where the desired timing is set to 0 degrees.

[HANK1948]

[QUOTE] [/What part of MI is the truck in? Near Holland? QUOTE]

No the truck is in the Detroit area...

[Slim shady]

JIM
I appreciate your help, I really need to have more info than a cryptic 1 step at a time with no explanation of why we are performing these steps ( desired outcome). I have already set the time at 3.5 and 4.2, not 3.0 like you replied and tried to get the TDC learn to set, no change.-2.02

Why would 3.5 and 4.2 not set the TDC learn and 3.0 will (I will do that though)

I also realize that nothing can be taken for granted, because you do not know what checks or adjustments I have done.

I have been working on vehicles for a long time (Working commission not salary, Time is money) and have been doing tune up and drive-ability on a number of different makes and models, not just a single brand (once again I don't know everything). That is why I joined this forum because of the people and their willingness to help each other.

SO a little more explanation would be great. If not, I appreceiate your help so far and thank you for your input.

It is just nice to have more people to bounce ideas off of without trying to establish who knows more than the other guy. I already admit I don't know everything (want to),just enough to pay the bills for the last 26 years. I will figure it out one way or another though.

Thanks

Slim

[Kennedy]

I'm trying to guide you there, but some times its simpler to just give/follow directions that explain the meaning of what you are doing. The meaning is often revealed duringthe procedure.

Basically, I know from experience that you need to have time set down at 3.5

[Slim shady]

Sorry about slaying your name. (very impolite of me )

How about if I call you and talk in real time, let you know what I have and have not been able to get from the scanner/ vehicle.I just don't want to make a career out of this vehicle.

The system is an OBD 1 System the old 12 pin connector, the vehicle is a 1995 Burb auto trans. Not the new OBD 2, The Master Tech is Very similiar to the TECH 2 I used in the dealer until I left.

And you may very well be right but I have done others with no problem. That is why I am perplexed over this vehicle. Trying to help someone out and then bang problem vehicle.

Thanks Slim
PS Very nice post, much information and have some new ideas from your info.

[rjschoolcraft]

Call him. He's very helpful.

[Kennedy]

So how does a 96 truck have OBD1?

A motorhome I can see, but a pickup?

You can call if you like, but I'm going to tell you what I did in the post. The phone goes in streaks around here (everybody calls at the same time and some seem to keep dialing/dodging voice mail till they get an answer :mad: but at the moment it's been quiet.

That said, if you get the voice mail, leave a message and I'll return your call...

On edit: I missed the note in the first post and thought it was the truck in Hanks signature.

[ 12-30-2005, 07:28 AM: Message edited by: kennedy ]

[Slim shady]

Just finished talking with Mr. K, got a lot of info and some possible reasons why we might be where were at.

I also want to apologize to him and anyone else publicly if my posts came across as short. I sometimes can be to blunt,although I don't mean anything by it.

Slim

[rjschoolcraft]

There are many of us on here with the same symptoms. smile.gif

[Kennedy]

Lets us know the outcome.

P.S. I'm the originator of short and blunt. Thought I had a patent, but... ;)

[Slim shady]

NOPE! you don't, ASK my other half, Always asking me if I don't have something to do out in the garage, GO figure :D I will let you know what happens, supposed to work on it today. Must be crazy to enjoy working on vehicles ALL the time. Thanks guys! :D

[Slim shady]

First , I have it set, at -1.94, Hurray

We warmed vehicle up checked base time in time set mode. read 14.6 actual. Set the base time while running (thanks JK) to 3.5 before TDC Measured. Checked TDC offset learn and came up with +2.2.

Shut vehicle off and moved pump to driver side. Started vehicle and measured base time in time set mode read 3.5 measured, did a TDC offset learn and came up with +.20. Rotated pump some more to the driver side and read base time 4.5 (time set mode). Did TDC learn and came up with -.20.

Moved pump to index mark, at this point we were still on the negative side of the index mark until the next try. Read base time as 7.5 (time set mode). Did tdc relearn and came up with -1.85 and when it hit -1.94 we stopped the learn procedure and saved the -1.94 as the TDC offset.

Runs much smoother and a lot less noise..

JK you were right, I did it in less than 15 Minutes, had to go back to the beginning to get to were I needed to be. Thanks,

Slim
PS, On a plus note, You also taught me something that I didn't know about that PCM. NOW that is worth something. How can I pay??

[Kennedy]

Glad you got it. Odd that Time Set was at 7.5

[HANK1948]

The only way we could get it to stay running when the pump was moved far enough to the passenger side to achieve the 3.0' was to have the "Fast Idle" switch on. So I assume when Slim is posting the 7.5' that was read when it was at 1075 rpm and that would create the advance...

Thanks to all for your insight and especially Slim for comin' by numerous times until we got it right...