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Ask GM Tech (Cam) Your Own Question

GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 27662
Experience:  GM Grand Master Technician 2007. 11 years experience.
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2001 chev s15 blazer,stall when i come to a stop

Customer Question

2001 chev s15 blazer,stall when i come to a stop
Submitted: 4 years ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 4 years ago.

Welcome to Just Answer and thank you for asking your question. I look forward to helping you fix your vehicle.

 

I will try my best to help you and in order to do that, I need you to describe the issue in as much detail because I only know as much about your vehicle as you have told me in your post, so my answer will be based on what you have posted. Please include all the small details that may seem insignificant such as warning light, codes that you have scanned and how this started. I will also try my hardest to help you avoid a dealer or shop, but with the modern vehicles an electronics, there may come a point that we cannot avoid this, and if that is the case, I will tell this.

My goal is your satisfaction and I ask that you not accept unless you are satisfied, but if you are satisfied, please accept so I can receive credit for my work and time. Positive Feedback is greatly appreciated and bonuses are always welcomed.

 

Please feel free to reply as needed.

 

Is the check engine light on? What is the mileage?

Customer: replied 4 years ago.

check engine light has been on evap codes, has had a new autotrans recently installed

has 169,000 miles on it.codes that are present p0449,p0452,p1639.I think what need is a diagnostic chart and a componet location chart related to evap system and or suggestions.

Expert:  GM Tech (Cam) replied 4 years ago.
OK, does it stall like stopping with a standard transmission while forgetting to press the clutch?
Customer: replied 4 years ago.
yes,but not while idling only after driving and comming to a stop
Expert:  GM Tech (Cam) replied 4 years ago.

Ok, this sounds like there is a problem with the torque converter clutch or the valving in the valve body.

I suggest you start by looking for a code P1870 in the computer. Also check the transmission pan for debris.

Customer: replied 4 years ago.
no code p1870 present,what about evap codes?
Expert:  GM Tech (Cam) replied 4 years ago.
They will not cause this issue. The p0449 is for the evap vent solenoid electrical circuit and the P0452 is the fuel tank pressure sensor. The P1639 is also related to the tank pressure sensor.
Customer: replied 4 years ago.
ok so evap system cant cause a stall,question is would eng die if i shift into nuetral before i come to a stop. converter gets taken out of play right?
Expert:  GM Tech (Cam) replied 4 years ago.
Yes, and that is what I was going to suggest next. If it does, still, then clean the throttle body, mass air flow senaor and check the air filter.
Customer: replied 4 years ago.
done all that,even istalled a known good maf sensor
Expert:  GM Tech (Cam) replied 4 years ago.
Have you tried swapping the idle air bypass valve?
Customer: replied 4 years ago.
yes
Expert:  GM Tech (Cam) replied 4 years ago.

Does it stumble with the brakes on period?

Customer: replied 4 years ago.
your thinkin brake booster right?no eng stuble when brake applied.
Expert:  GM Tech (Cam) replied 4 years ago.
Yes, ok no stumble. Boy I wish I could see what is happening on a scan tool when this happens. Do you have access to a scan tool?
Customer: replied 4 years ago.
yes a snap on scanner only goes to 98,but i can go in to generic or vin to a 98
Expert:  GM Tech (Cam) replied 4 years ago.
If it will give a data stream then perhaps. I don't use that scan tool so I cannot say for sure.
Customer: replied 4 years ago.
yes it will
Expert:  GM Tech (Cam) replied 4 years ago.

Ok, lets see what the crank signal, throttle position, MAP and MAF sensor do as it is stalling, not after it stalls.

Customer: replied 4 years ago.

cant read signals fast enough to get sound readings

Customer: replied 4 years ago.
could broken motor mounts create this problem,both are broke
Expert:  GM Tech (Cam) replied 4 years ago.
I doubt broken motor mounts. What is the MAP reading at idle and the IAC counts?
Customer: replied 4 years ago.
2.84 v 19hg map,IAC 0 counts im wondering if its goin iinto closed loop o2 sensor b2-s1 no (mv)
Expert:  GM Tech (Cam) replied 4 years ago.
Ok, IAC, 0 is bad. It should be 35-40.
Customer: replied 4 years ago.
ok that makes sence,I have checked voltage to Iac all ok, I should have some kind of reading open or closed loop right and what about the o2 sensor i mentioned.Iac has been replaced install procedure followed.
Expert:  GM Tech (Cam) replied 4 years ago.
I noticed the sensor reading. I suggest you test the wiring between that sensor and the PCM. If you find no issues and there are no vacuum leaks, then you might be looking at a bad PCM.
Customer: replied 4 years ago.
you mean on the Iac to pcm?
Expert:  GM Tech (Cam) replied 4 years ago.
IAC is the idle Air bypass. PCM is the Powertrain control module or the engine computer.
Customer: replied 4 years ago.
got continuity threw all wires from pcm to Iac
Expert:  GM Tech (Cam) replied 4 years ago.
Is there continuity to ground with those wires disconnected? How about the oxygen sensor wiring?
Customer: replied 4 years ago.
no continuity to ground,I have pcm and iac disconnected ,havent checked o2 wireing yet.Shouldnt there be continuity between related posts on pcm
Expert:  GM Tech (Cam) replied 4 years ago.
There may be resistance between terminals inside the PCM but that's not a good way to check it because of the solid state devices inside. Check the oxygen sensor wiring to the PCM and let me know what you find.
Customer: replied 4 years ago.
ok,could you send me a break out diagram of wireing from o2 to pcm
Expert:  GM Tech (Cam) replied 4 years ago.

Object Number: 669498  Size: FSClick

Customer: replied 4 years ago.
o2 sensor wiring is good
Expert:  GM Tech (Cam) replied 4 years ago.
Then it may be the PCM.
Customer: replied 4 years ago.
found a used pcm but they tellin me it needs reprogramed,what does that concist of?
Expert:  GM Tech (Cam) replied 4 years ago.
They need to program it using programming software to your VIN and then you need to do a theft relearn. It should take about an hour at a shop.
Customer: replied 4 years ago.
does that need to be done before install on the programing,also can my pcm verified for a problem with same software?
Expert:  GM Tech (Cam) replied 4 years ago.
Unfortunately verifying the PCM as the issue is more a process of elimination. Is this case we believe that the wiring is good, the sensors are new so what is left? Unless there is something that you have not told me, I think it is a good chance of being the PCM. Some places can program before installation.
Customer: replied 4 years ago.
the only thing i left out was previous problem with fuel pump and sending unit,specificly fuel guage inop. found broked bared wires, that i repaired there was also a blown ecm1 fuse installed new one maintains voltage both sides of fuse. this problem occured shortly after.Didnt think it was important mayby it is now!
Expert:  GM Tech (Cam) replied 4 years ago.
I don't think that has anything to do with this.
Customer: replied 4 years ago.
mayby not,the reason wires got screwed up is because trans shop did not secure them properly when they installed trans.
Expert:  GM Tech (Cam) replied 4 years ago.
Ok.
Customer: replied 4 years ago.
seems quentcidental this all started after the install
Expert:  GM Tech (Cam) replied 4 years ago.
If you are certain the wiring is not bad then what can I say. I am relying on your observations and testing.
Customer: replied 4 years ago.
ok,just able to get back to my problem child.Im rechecking voltage on IAC LTGRN/BLK&LTBLU& BLK HAVE 10.5 V. LYGRN/WHT&LTBLU&WHT HAVE 0.47 V . ARE THEASE CORRECT ?
Expert:  GM Tech (Cam) replied 4 years ago.
I have never tested that way. We test by controlling the idle with the scan tool. If the idle responds, then it is good. If not, then we use a tester often sold in a Noid light set that plugs into the connector.
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 27662
Experience: GM Grand Master Technician 2007. 11 years experience.
GM Tech (Cam) and 2 other Chevy Specialists are ready to help you
Customer: replied 4 years ago.
I have 2 post niod lights that work,if whats the test procedure? with scanner no control or IAC reading
Expert:  GM Tech (Cam) replied 4 years ago.
No there is a special noid light for the IAC, has 4 terminals.
Customer: replied 4 years ago.
i have another question reguarding this 01 blazer,If iac was not functioning would there be fast idle when cold( first start) and then idle down as it warms up?
Customer: replied 4 years ago.
waiting for reply on last question.
Expert:  GM Tech (Cam) replied 4 years ago.

No, I suspect that what you describe is normal. High idle to get things warmed up and idles down to desired as it is warned up and in or near closed loop.

Customer: replied 4 years ago.
so Iac is working, yet i have a stall issue still when coming to a stop our last diagnoses was a possible pcm problem. im not so sure that the problem?
Expert:  GM Tech (Cam) replied 4 years ago.
Honestly I am not sure either. Because I cannot see the live diagnosis or scan tool data, I am not sure that we will be able to, and it is because the Internet is not a good way. If you wish I will refund your money as I feel that we will not get to the bottom of this.
Customer: replied 4 years ago.
no need to refund,you have put your time into this problem.now i have noticed that if i come to quick stop eng will stall and fuel guage goes to empty,If i come to a slow stop it does not do this?A fuel module sending unit has been replaced also there were some bared wires on the fuel pump harness near transmission that were rubbing on front drive line.Could this have caused damage to PCM in some way sence all goes through PCM?
Expert:  GM Tech (Cam) replied 4 years ago.
It is rare that a problem on a circuit to the PCM such as this will damage the PCM as there is usually internal protection.
Customer: replied 4 years ago.
ok,stall problem cured,now im trying to diagnos evap problem,codesp0449,p0452,p1639.Ive replaced fuel cap so far all evap lines appear to be ok
Expert:  GM Tech (Cam) replied 4 years ago.
{P0449 is wiring to the EVAP vent solenoid and the P0452 is the fuel tank pressure sensor on the top of the pump asembly.
Customer: replied 4 years ago.
ok,pressure sensor was replaced with fuel module, evap vent solenid its located on engine near oil fill cap right? what does p1639 5v ref low tcm a/d fault tellin specifically tcm a/d fault?
Expert:  GM Tech (Cam) replied 4 years ago.

No the vent is near the tank above the spare tire.

Object Number: 747560  Size: SH

The P1639 is the 5V feed for the tank pressure sensor. The chart goes through and indicates either a problem with the wiring, sensor or the PCM.

Customer: replied 4 years ago.
ok i know which one that is ive seen it,so if it has 5v ref and all wireing looks good then that sensor is bad? could i get wireing diagram for that circut
Expert:  GM Tech (Cam) replied 4 years ago.
Object Number: 669493  Size: FS
Customer: replied 4 years ago.
ok,wires at FTP are pink has 4.79v white 1.67v not same as whats on diagram
Expert:  GM Tech (Cam) replied 4 years ago.

The sensor has 3 wires, not 2.

Pink and white sounds like the vent valve not the pressure sensor.

Customer: replied 4 years ago.
ok,where are you saying the pressure sensor is?
Expert:  GM Tech (Cam) replied 4 years ago.
Object Number: 64998  Size: SH
Customer: replied 4 years ago.
ok,that was replaced with fuel pump module so must be a electrical issue send diagram for that plz
Expert:  GM Tech (Cam) replied 4 years ago.

The wiring diagram I sent has that sensor in it.

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