yes it seams so had signal with just pcm and with pcm+ bcm and with comb in. but still no data link up my scanner worked on my 97 Sonoma it is running well but it links up and some thing new (recap this started with me getting blazer with starter broke off block so replaced block timeing chain bearings and so forth) it had crazy dash from the time it was back together yesterday the key was sticking and today it was being a pain key sticking (maybe ignition switch)? i have a 5g samsung smart phone what what blutooth scanner do you recomend and a inexpensive automotive oscilloscope do you recommend

 

There are a couple of things to decide before buying an oscilloscope.

1. How many channels
2. Portable and battery powered, desktop, or interface module for a laptop or desktop pc
3. Ability to look at high voltage waveforms

For a diy shade tree mechanic, 2 channels is good enough but more channels help with some things. The little battery powered ones are convenient and can do the low voltage stuff:


but I don’t know if they can work with inductive high voltage probes for looking at secondary ignition:




A traditional desktop unit can use those probes and can do most things:




an interesting option that I have not tried is an interface box that accepts probes and sends the waveforms to say a laptop for viewing. Because it has traditional bnc connectors it should work with high voltage inductive probes and it looks rugged but then you have a pc perched somewhere near your work:




I have that first portable scope and it works pretty good but I don’t know if it does high voltage waveforms because of the little SmA type connectors. That desktop scope is a common budget recommendation but there are cheaper alternatives like Hantek but I have no experience with Hantek. Again that interface unit is interesting but I have not tried it. My desktop scope is a Sigilent which is also pretty good and I use those inductive probes but it’s a pain to bring to the truck and it’s not very rugged. I am going to try that interface box some day.

As far as BT scanners, one of the best dongles is:


which is what I use. As far as software there are a few we recommend here:

https://blazerforum.com/forum/2nd-ge...lazers-103424/

The three wildcards on these scanners is the ability to monitor CMP retard, custom GM PIDs and decent graphing for say O2 sensor monitoring.


George

 

George i may have found something a few days ago my key felt funny then today i googled my dash symptoms and found this on our blazer form it is exactly what my car is doing however i checked pin 13 on the c4 plug and it has power 12 volts in the run position

Old 12-18-2006, 09:55 PM
lastcoupe
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Default RE: TSB #3777 - How can I get the detailsHere's what you are looking for (I think....lol):







Subject:
Fuel and Temperature Gauge Inoperative, Low Fuel and Battery Light On, PRDNL Inoperative - keywords charge cluster dash electrical fuse generator indicator IPC lamp voltage wire #PIT3777 - (11/10/2005)

[align=left]



Models:
1998-2000 Chevrolet S-10 Pick Up and Blazer [/align][align=left]




1999-2000 Chevrolet Silverado [/align][align=left]




1998-2000 GMC Sonoma and Jimmy [/align][align=left]




1999-2000 GMC Sierra [/align][align=left]




1998-2000 Oldsmobile Bravada [/align][align=left]




Equipped with 4.3L L35 only [/align]


[hr]

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
The fuel gauge and temperature gauge are inoperative and the low fuel and battery lights are on. The PRNDL indicator is inoperative on A/T vehicles. These symptoms can be intermittent. When using a scan tool the inputs are normal when viewed on the powertrain data list, but read zeros when viewed in I/P data list. The gauges will sweep when using the scan tool. This can be caused by an open in circuit 241 to the VCM connector C4 pin 13. This is the ignition 3 feed to the VCM. It is one of the inputs used to determine the ignition lock/switch position. When this circuit is open the VCM sees the switch as always in the crank position, while in this mode the class 2 serial data is in a reduced function state, the Tech 2 will still communicate with the various modules and no DTCs will set.
The following is a matrix indicating what inputs are used to determine the ignition switch position at the VCM.
Position

Ignition 0

Ignition 1

Ignition 3


Unlock

B+






Run

B+

b+

b+


Crank

B+

b+


Recommendation/Instructions:
Check for B+ at VCM connector C4 pin 13, this circuit 241 should only have battery voltage when the ignition switch is in the run position.
Note:Both the 2 wheel drive and 4 wheel drive S/T vehicles with a 4.3 L engine use fuse #15 (4WD) in the IP fuse block and the related wiring (circuit 241) to the VCM for this crank input.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.





GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

 

I think that you should check all the powers and grounds for the engine computer and BCM but before I start listing the connectors and pins, what year is the truck, it this the original wiring harness for that truck model year, and the engine is a 2000 correct?

George

 

yes i changed out the block but all the parts except starter are original the intake and injectors are original fuse box wiring all came with the car i did put a new timing chain in it but i would say its all original somebody did put a new radio in it the date is 05 / 00 VIN1GNCS13W5Y2374608

 

OK. I’m out of town today but I’ll get you your powers and grounds when I get home tonight George

 

Power:

BCM:

C1/A2 Org
C1/B2 Pnk (run)
C1/B9 Brn (run or start)

VCM:
C3/21 ORG
C4/13 Brn (run)
C4/17 Pnk (Ign)
C4/18 Pnk (run or start)

Grounds:

BCM:

C1/A1 Blk
C1/B1 Blk

VCM:

C3/17 Blk/Wht
C3/18 Blk/Wht


George

 

i am thinking org is always 12 volt

run is 12volt when key is on run

run or are both 12 volt in both positions

not sure about ign its not the same as run ?

 

Same here.

 

just a quick update started checking vcm power and ground looks good but mosquitoes and darkness came will check bcm and post results thanks again for all the help