2000 blazer wont scan bcm?
#11
10-31-2012, 03:18 PM
Fuel test passed flying colors. 60 psi... lost 3 psi over ten mins.
replace bcm and pcm, and did relearn. Vehicle starts and runs fine at idle.
same issue. will not run above idle, and Still my scanner will not read the PCM!! SIGH!!
I cant see data stream, will not read dtc's... nothing.. Going to double check powers and ground on PCM/ engine wire harness,.
Have not checked cap, thanks, but even a cracked or shorting cap would backfire pop or miss. It runs fine at idle. jut doggs down when try to open throttle.. no power.
Tells me lack of fuel or timing. no cat in car. exhaust flows good. intake clear. I wish I could read this PCM!
/rant off
Dodgeman
PS thanks all for your consideration and help.
replace bcm and pcm, and did relearn. Vehicle starts and runs fine at idle.
same issue. will not run above idle, and Still my scanner will not read the PCM!! SIGH!!
I cant see data stream, will not read dtc's... nothing.. Going to double check powers and ground on PCM/ engine wire harness,.
Have not checked cap, thanks, but even a cracked or shorting cap would backfire pop or miss. It runs fine at idle. jut doggs down when try to open throttle.. no power.
Tells me lack of fuel or timing. no cat in car. exhaust flows good. intake clear. I wish I could read this PCM!
/rant off
Dodgeman
PS thanks all for your consideration and help.
#12
10-31-2012, 06:13 PM
After you replaced the PCM:
Did you have it flashed to your VIN? (mandatory)
Did you perform the crankshaft position sensor relearn? (mandatory)
Did you check/adjust camshaft retard? (mandatory to make sure ignition timing is correct)
Did you have it flashed to your VIN? (mandatory)
Did you perform the crankshaft position sensor relearn? (mandatory)
Did you check/adjust camshaft retard? (mandatory to make sure ignition timing is correct)
#13
11-01-2012, 10:17 AM
Crank relearn: NO. Scan tool will not communicate. Vehicle will not run above idle.
Cam Retard: NO. Scan tool will not communicate with PCM.
Your words, timing light is garbage. Fine. I still am reading around the internet to learn exactly what is need for a cam retard and how to set it. Without a scan tool.
OK. History time. Vehicle ran ok for years. Had misses because my sis refused to give it a tune-up. One month ago it started really having problems. MPG dropped, low power, barely drivable.. had to feather the throttle to gain any speed. then after she stopped at a intersection, it really wouldn't move.
So she limps it to my house. And expects miracles. (yeah, irrelevant. Apologies.) But my point is this vehicle starts and runs. Compression good, I did tune up, plugs wires and washed IAC and TB Housing. Basic Stuff.
No improvement. Well. I fixed the missing cylinders. But still runs bad. It barely has the power to move on level ground.
Lord knows I am trying to scan this bugger, if only to verify what works /what isn't. But so far I haven't been able to.
Meanwhile, I refuse to do nothing. My experience tells me it feels like a blocked exhaust. I know the cat is gone, (straight pipe).
Or it has to do with timing!
Since I can't check one, Ill check the other.
And Lo and behold, Another lost soul with a vehicle running like mine replace $1000 dollars worth of stuff to no help and 3 trips to different dealers found a bad Y- pipe in his exhaust! Apparently it is double walled and the internal pipe had collapsed. It was spotted thru the Oxy sensor hole. I have a date with mine, and will let u guys know.
Dodgeman.
Last edited by Dodgeman; 11-01-2012 at 12:20 PM.
#14
11-01-2012, 04:31 PM
Update!
Thanks all who responded and those that took time to read this.
I found the problem with the vehicle. The Running issue that is.
In my peering under the vehicle I didnt see the catylytic converter hiding behind the transfercase. I saw pipe on one side and muffler the other.
to test I pulled a Oxygen sensor from in front of the cat leaving a open hole and started vehicle. Immediately I have a huge difference! The cat was well and truly plugged!
Now I have the cat off the vehicle I started it again and verified proper throttle response, timing advance and fuel rate, (by ear!) darn this confounded vehicle.
Putting the exhaust back together.
I wish I had a final answer as to why I couldn't scan this vehicle, to help others. $100 bucks for a used PCM and $33 bucks for a used BCM, didn't help at all. Something is amiss, I regret buying my OTC 4000e, the Scanner to end all scanners! Bloody thing cost 1500 bucks in 92. when they stopped supporting it, the only expansion kit was 600 bucks, wich only got us to 95, or there-abouts. OBDII is here but I been stung before. This acctron 9145 was 400 bucks 5 -7 years back and it was there best scanner at the time, and it clearly cant read half what I expected to pay for. (Like BCM, ABS and the rest of the vehicle.)
Probably if you got the money your best bet is to buy a used recent model scanner online, Fix your vehicle, then sell your scanner and recoup your money. Wish I wasn't so broke.
Anyways, tips from me, to find out if you got a plugged exhaust, pull a oxy sensor out in front of your cat and turn the key!
Fast and cheap way to test your exhaust. you'll notice a significant difference!
Swapping out a used BCM. I did. I didn't flash it either. But this BCM could be from a large variety of vehicle (pick up, vans)... so try to get one close to your vehicle with same options.
Swapping PCM... I did, and the vendor was able to pre-flash it according to vin code before He shipped it out. And while I had to do the passlock relearn, (to teach the truck I wasn't stealing it by installing a different brain (brilliant!!)
it was able to run the engine just fine. I didn't crank relearn (couldn't + Can't) And I didnt Cam retard (Same).
I wish you all well
Dodgeman.
Thanks all who responded and those that took time to read this.
I found the problem with the vehicle. The Running issue that is.
In my peering under the vehicle I didnt see the catylytic converter hiding behind the transfercase. I saw pipe on one side and muffler the other.
to test I pulled a Oxygen sensor from in front of the cat leaving a open hole and started vehicle. Immediately I have a huge difference! The cat was well and truly plugged!
Now I have the cat off the vehicle I started it again and verified proper throttle response, timing advance and fuel rate, (by ear!) darn this confounded vehicle.
Putting the exhaust back together.
I wish I had a final answer as to why I couldn't scan this vehicle, to help others. $100 bucks for a used PCM and $33 bucks for a used BCM, didn't help at all. Something is amiss, I regret buying my OTC 4000e, the Scanner to end all scanners! Bloody thing cost 1500 bucks in 92. when they stopped supporting it, the only expansion kit was 600 bucks, wich only got us to 95, or there-abouts. OBDII is here but I been stung before. This acctron 9145 was 400 bucks 5 -7 years back and it was there best scanner at the time, and it clearly cant read half what I expected to pay for. (Like BCM, ABS and the rest of the vehicle.)
Probably if you got the money your best bet is to buy a used recent model scanner online, Fix your vehicle, then sell your scanner and recoup your money. Wish I wasn't so broke.
Anyways, tips from me, to find out if you got a plugged exhaust, pull a oxy sensor out in front of your cat and turn the key!
Fast and cheap way to test your exhaust. you'll notice a significant difference!
Swapping out a used BCM. I did. I didn't flash it either. But this BCM could be from a large variety of vehicle (pick up, vans)... so try to get one close to your vehicle with same options.
Swapping PCM... I did, and the vendor was able to pre-flash it according to vin code before He shipped it out. And while I had to do the passlock relearn, (to teach the truck I wasn't stealing it by installing a different brain (brilliant!!)
it was able to run the engine just fine. I didn't crank relearn (couldn't + Can't) And I didnt Cam retard (Same).
I wish you all well
Dodgeman.
#15
11-01-2012, 04:35 PM
The crankshaft position sensor emits a magnetic field directed at the tone ring on the front of the crankshaft:
As the teeth pass the sensor, the field is interupted and the sensor sends a pulse to the PCM. The field is focused toward the tone ring and the relearn procedure synchronizes the exact position of the field with the tone ring pulses. The PCM now "knows" the exact position of the crankshaft. The synchronization data is burned into a memory file in the PCM and can not be deleted or modified until another relearn is performed. If the PCM is replaced, (disconnecting the battery has no affect on sync data) the crankshaft position sync data is incorrect. In the case of a new PCM, a default value is used so the engine will at least run so the relearn can be done. If the PCM is used or refurbished, the sync data will be incorrect. In either case, ignition timing, injector timing, RPM, etc, will all be affected causing driveability issues.
The camshaft position sensor is a Hall Effect switch, which is an extremely acurate electronic switching device located in the distributor.
Rotating the distributor precisely aligns the sensor with the camshaft, hence the name. It also aligns the rotor with the terminals inside the cap to reduce/prevent crossfire in the cap. Camshaft retard is viewed in degrees using a higher end scan tool, the $300 or $400 el cheapos can't access it. Some computer software programs are able to access the streaming data. Camshaft retard has a direct affect on ignition timing: The amount of degrees that it's off, is the amount of degrees that ignition timing is affected. For example: If the PCM applies +15 degrees advance, if camshaft retard is -15 degrees, you end up with zero degrees advance. If camshaft retard is off more than ~27 degrees, the check engine light will come on and DTC P1345 will be set in memory. Bottom line is, ignition timing could be off up to 26 degrees, in either direction, and no check engine light. The PCM "assumes" camshaft retard is correct, and it applies ignition timing as it is programmed to do in each situation. It's the technicians job to make sure it's correct
The crankshaft position sensor data along with the camshaft position sensor data is used by the PCM for detecting misfires and identifying which cylinder(s) are misfiring. If either sensor is not reporting acurate data, misfire data on the scan tool will not be acurate. If the crankshaft position sensor data is interrupted, the engine will not run. If the camshaft position sensor data is interrupted, or the sensor is unplugged, you may or may not notice a difference in performance, but cylinder misfire will not be detected.
The relearn must be done first, then check/adjust camshaft retard. Those are basics with this engine, and they must be correct.
As the teeth pass the sensor, the field is interupted and the sensor sends a pulse to the PCM. The field is focused toward the tone ring and the relearn procedure synchronizes the exact position of the field with the tone ring pulses. The PCM now "knows" the exact position of the crankshaft. The synchronization data is burned into a memory file in the PCM and can not be deleted or modified until another relearn is performed. If the PCM is replaced, (disconnecting the battery has no affect on sync data) the crankshaft position sync data is incorrect. In the case of a new PCM, a default value is used so the engine will at least run so the relearn can be done. If the PCM is used or refurbished, the sync data will be incorrect. In either case, ignition timing, injector timing, RPM, etc, will all be affected causing driveability issues.
The camshaft position sensor is a Hall Effect switch, which is an extremely acurate electronic switching device located in the distributor.
Rotating the distributor precisely aligns the sensor with the camshaft, hence the name. It also aligns the rotor with the terminals inside the cap to reduce/prevent crossfire in the cap. Camshaft retard is viewed in degrees using a higher end scan tool, the $300 or $400 el cheapos can't access it. Some computer software programs are able to access the streaming data. Camshaft retard has a direct affect on ignition timing: The amount of degrees that it's off, is the amount of degrees that ignition timing is affected. For example: If the PCM applies +15 degrees advance, if camshaft retard is -15 degrees, you end up with zero degrees advance. If camshaft retard is off more than ~27 degrees, the check engine light will come on and DTC P1345 will be set in memory. Bottom line is, ignition timing could be off up to 26 degrees, in either direction, and no check engine light. The PCM "assumes" camshaft retard is correct, and it applies ignition timing as it is programmed to do in each situation. It's the technicians job to make sure it's correct
The crankshaft position sensor data along with the camshaft position sensor data is used by the PCM for detecting misfires and identifying which cylinder(s) are misfiring. If either sensor is not reporting acurate data, misfire data on the scan tool will not be acurate. If the crankshaft position sensor data is interrupted, the engine will not run. If the camshaft position sensor data is interrupted, or the sensor is unplugged, you may or may not notice a difference in performance, but cylinder misfire will not be detected.
The relearn must be done first, then check/adjust camshaft retard. Those are basics with this engine, and they must be correct.
Last edited by Captain Hook; 11-01-2012 at 04:42 PM.
#16
11-01-2012, 09:26 PM
Solved, Sorta Vehicle is running ok. Plugged Cat. Converter.
Hello there. I am working on this 2000 blazer (sister's), and its having issues.
It runs semi-well at idle, but has no power when the throttle is depressed. I did all the normal check first, It needed new plugs, wires (was original 150k mi) and fuel filter, Cat converter was replaced with a straight pipe long ago and flows good amount of exhaust. Washed throttle body and IAC valve, and checked idle vac 14 inches. so.
engine runs a little rough, but not horrible at idle, like it has for years. but try to step on it causes it to bog down, like a blocked cat or weak fuel system.
I checked fuel pressure, 60 psi and delivery, its a-ok. so I am thinking mebbe a bad sensor or such might be causing the pcm to not advance the engine timing.
Now, I connect my scan tool to the vehicle, and I get nothing. Reading up on Swartlkk's articles, I think I need to swap my BCM out in order to read the pcm, because I have the correct volts on pin 16 of the odb2 connector, pins 4+5 have good grounds, but pin 2 I get 0 volts in a steady flashing pattern. it trys to read something, but falls to zero.
I did the steps of disconnecting the sp201 splice, and connecting only the bcm up and with only the bcm and pcm, but no change. the wiring is intact and not shorted, I even test power and grounds to the bcm. but my scanner wont read it.
The next step is replace BCM. But I have a question. My old scanner, Acctron super 9145, is a few years old, is obd2, and when I connect it tries to "connect" to PCM/VPCM, and it is waiting forever. I know the scanner works on other odb2 vehicles, But I wonder that since I been reading a ton of info about scanners that wont read abs and other such modules, if I am barking up the wrong tree before I order a replacement bcm, Sigh, so I can finally scan the vehicle and see whats wrong?
Thanks for any help.
Dodgeman
It runs semi-well at idle, but has no power when the throttle is depressed. I did all the normal check first, It needed new plugs, wires (was original 150k mi) and fuel filter, Cat converter was replaced with a straight pipe long ago and flows good amount of exhaust. Washed throttle body and IAC valve, and checked idle vac 14 inches. so.
engine runs a little rough, but not horrible at idle, like it has for years. but try to step on it causes it to bog down, like a blocked cat or weak fuel system.
I checked fuel pressure, 60 psi and delivery, its a-ok. so I am thinking mebbe a bad sensor or such might be causing the pcm to not advance the engine timing.
Now, I connect my scan tool to the vehicle, and I get nothing. Reading up on Swartlkk's articles, I think I need to swap my BCM out in order to read the pcm, because I have the correct volts on pin 16 of the odb2 connector, pins 4+5 have good grounds, but pin 2 I get 0 volts in a steady flashing pattern. it trys to read something, but falls to zero.
I did the steps of disconnecting the sp201 splice, and connecting only the bcm up and with only the bcm and pcm, but no change. the wiring is intact and not shorted, I even test power and grounds to the bcm. but my scanner wont read it.
The next step is replace BCM. But I have a question. My old scanner, Acctron super 9145, is a few years old, is obd2, and when I connect it tries to "connect" to PCM/VPCM, and it is waiting forever. I know the scanner works on other odb2 vehicles, But I wonder that since I been reading a ton of info about scanners that wont read abs and other such modules, if I am barking up the wrong tree before I order a replacement bcm, Sigh, so I can finally scan the vehicle and see whats wrong?
Thanks for any help.
Dodgeman
#17
11-02-2012, 12:54 PM
I'm a bit confused here... How does the restricted converter affect the running of the vehicle if it isn't installed on the vehicle???????
#18
11-02-2012, 03:12 PM
well, thanks fer asking. I looked under the vehicle on the wrong side of the truck. hidden behind the transfer case was the cat. I saw pipe on one side and flange on the other. didn't see it hiding so well. I was going to unbolt the y off the engine to see if there was an obstruction and got a better view.
Soon as I saw the cat I knew what it was. Mid way to loosening the manifold bolts trying to be gentle around the oxy sensor, I knew I had a simple test hole right there!
So tighten back up those bolts and pop the sensor out, and test the engine. Voila!
P.S.: i respect your opinion that the relearns should be done, for mileage and drivability. But i am happy to report I didnt. and for me the truck is running fine, the check eng light is out and many items the bcm wasnt doing now work. it has tons of get up and go and and sis can drive it to a dealer if she wishes. (fat chance)
thanks!
Soon as I saw the cat I knew what it was. Mid way to loosening the manifold bolts trying to be gentle around the oxy sensor, I knew I had a simple test hole right there!
So tighten back up those bolts and pop the sensor out, and test the engine. Voila!
P.S.: i respect your opinion that the relearns should be done, for mileage and drivability. But i am happy to report I didnt. and for me the truck is running fine, the check eng light is out and many items the bcm wasnt doing now work. it has tons of get up and go and and sis can drive it to a dealer if she wishes. (fat chance)
thanks!
#19
11-02-2012, 03:18 PM
Thanks, got it Things just weren't clicking.
You'd be surprised how well it would run with the relearn & cam retard done.
Things just weren't clicking.You'd be surprised how well it would run with the relearn & cam retard done.
Thread
Thread Starter
Forum
Replies
Last Post
vic98blazer
2nd Generation S-series (1995-2005) Tech
5
02-23-2012 05:34 PM
jimpasq57
2nd Generation S-series (1995-2005) Tech
5
11-06-2011 07:55 AM
