Using a "GYMKO" Tech2 for Post R&R Testing of a GM Repaired Instrument Cluster

MRRSM

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#1
This is an interesting Instrument Panel Cluster Rebuild-Repair Job involving a Professional Re-Fitter of Instrument Clusters receiving essentially a Bag of FUBARed Cluster Components from one of his embarrassed Customers and then essentially performing an UN-FUBAR job and an R&R of misplaced, missing or damaged Stepper Motors. This kind of video is nothing new to those who have had to perform this repair. But what is particularly interesting is the way the E-Tech uses his "GYMKO" Tech2 Scanner to run Bench Top Post Diagnostics to show whether or not his work was successful.

What is Cool also about this video is that this Dude sort of "lifts his skirts" a little to show a separate Homemade Diagnostic Harness that includes the OEM Vehicle Cluster Connector AND a separate OBD2 DLC Connector mated up with some sort of a Half-Assed Wire Breadboard job to allow the use of his "GYMKO" Tech2 to run some neat Bench Tests. I have not looked over any of his other videos to see if he describes how he built this Instrument Cluster-To-Tech2 Powered Test Harness... but it sure would be nice to have one of these for doing these kinds of repairs.

I cannot say that I would blame him for sitting on the secret... as he would be shooting himself in the foot business-wise if the rest of us "GYMKO" Owners knew how he did it. If we have any Members with the 'E-Circuit Savvy' to watch his videos and sort of dope out his Wire Harness connections and choices... perhaps we can reverse engineer it here and then be able to buy the inexpensive OEM IC & OBD2 Connectors and make our own versions of it. Nonetheless... Even if you just did the solder repairs and then plugged it right back into the Truck Harness Cluster Connector... you could power up the Cluster in the Truck B4 completely re-assembling it inside of the Cluster Case... and use Your Own "GYMKO" Scanner to run those very same tests after fixing the Dial Gauges and know for certain...all works well. This would be a very cool thing to be able to do! Many Thanks to the VOP for showing us yet another way to use our "GYMKO" Hand Held Scanner(s). :>)


This Attached Image is for the 2004 Instrument Cluster Wiring Schematic for future reference during soldering repairs... (Click on the Image to Enlarge it):

2004 trailblazer instrument cluster wiringcolor.jpg
 
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MRRSM

MRRSM

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#2
While this idea of running Diagnostics on the Instrument Cluster using the Electrical Harness Connector is just too good to pass up… it seems that something similar could be Doped Out for the One, Two or any Necessary Combination of All Three P10 Style Connectors on the GM 4.2L PCM … and this following set up shows great promise that this could be accomplished if the proper Three Connector Pin-Outs and Power Connections can be translated over to this OBD2 Port Harness Connector as shown in this layout. If sorted out correctly… this same kind of Bench Harness for the GM Tech2 (GYMKO) Hand Scanner for the Bench Top examination and Re-Flashing of the LL8 PCMs should function nicely as a “GYMKO” Tech2 Interface ...IF… Only The Four Wire and Power Supply Connections covered below are the Barest Necessities Required to Make It Work:

This is a “How To Build” of a Generic GM LS Style PCM-To-OBD2 Bench Top Test-FLASH Harness as listed at the below link.

Disclaimer:

For my own understanding… It was necessary to edit the writing and expressions (but not the content) of this material over to a common standard for describing all of these components and their connections, as I found the original writing very difficult at times to decipher. I make no Claim to being the Originator of these Ideas, Designs or the attached Images and all First Person References that follow in the text pertain strictly to those of The Original Author and Creator of All This Material.

If you prefer reading the Author’s original text... it can be found here:

https://sites.google.com/site/sloppywiki/tuning-information/obd2-bench-harness

Sloppy Mechanics Bench Flashing harness build sheet and instructions for obd2 (blue red/green) style LS ecu's (and some more)”

Components:
1. 12-19 VDC Power Supply, 1amp min ( I have used 500ma, but would recommend staying above One Amp

a. These are very easy to find in old hardware, chargers, external computer components like hard drive enclosures and modem power supplies etc.
b. I have tested 12-19 volts without a problem, that being said, I would stay closer to 12-14 VDC as this is Voltage Levels that most cars use.

2. GM Blue ECU/ECM/PCM(80 Pin Connector)

a. This Connector directly interfaces the ECU.
b. The Connector is usually held in place with a 7mm Bolt to prevent Accidental Disconnection during FLASH and avoiding Unplugging and Bricking anything.

3. In-Cab OBD2 Connector

a. These can be found in JY inside GM Blazers and Cavaliers and so are already Pinned for GM ECMs.
b. Make certain it has Orange, Black and Purple Wires. If so… The rest is EZ.

Component Assembly:

1. On the Power Supply, strip the wires and test them with a Volt Meter to ensure that it works.

2. You’ll have to flip the connector’s wire side towards you. On the BlueECU Connector wherePin 1 is located in the upper left corner, Pin 20 is located at the Far End of that same Row. Pins 41-60 are likewise located on the Bottom Row. Only 4 Pins are necessary for this to function … the rest can remain in there, or they can be de-pinned to clean everything up.

3. Position the OBD2 Port Connector, with the Wider Side Facing Up and the wire contact points facing you displayed as Pins 1-8 situated at the top, and Pins9-16 located at the Bottom. You are only using 4 wires on this Connector…with the others mentioned below dedicated to the 12 VDC issues.

4. Take the Positive Power Wire from the Power Supply, and connect it to Pins 19 and 20 on the Blue ECU Connector, (in the Upper Right Two Pins) and then connect it to the OBD2 Portat Pin 9 (Located at Bottom Left).

5. Then take the Ground Wire and connect it from the Pin 1 (upper left) on the Blue ECU Connector over to Pins4 and 5, (upper middle) on the OBD2 Port Connector.

6. Then take the Purple Serial Data Wire and connect it from Pin 58 on the Blue ECU Connector(lower right side) over to the OBD2 Port Connector Pin 7 (upper right side)

Now before doing anything else, Plug it in and see if you can access the ECU with whatever you are using on the OBD2 Side. Ifyou can Connect/Read/Write,then You Are Set.


In Brief… USING JUST THE FOUR WIRES and the POWER SUPPLY CONNECTIONS:

Connect the 12VDC (+) Power Wire over to OBD2 Port Pin 9 (Orange) and to Blue ECU Pins 19 and 20 (Pink/Red)
Connect the Ground (-) Wire from the OBD2 Port Pins 4-5 over to Blue ECU Pin 1
Connect OBD2 Port Pin7 (Purple) over to Blue ECU Pin 58 (Serial Data Line)

Done!

Note:
As shown in the Image…Pin 60 does NOT need to be used (It was attached during testing and just left it in there). The same applies to Pin 16 (Brown Wire on the OBD2 Port) ...as it was clipped off during the JY Claim and it was just never de-pinned.
 

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MRRSM

MRRSM

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#3
This is a bit of a H/J of my own thread... But I want to eventually try to make contact with this VOP and see if he will spring for a Free Wiring Diagram of his Home Made "GYMKO" to OBD2 to Instrument Cluster Harness Wiring and Component Schematic and since his Skill Set is something that we value very highly over here at GMTN... It might be nice if some of our folks paid a visit to his Youtube Channel and Joined if possible so he can bounce over 1,000 people and keep his monetization level now that Youtube has stricter rules in playing in their ball park.

Just take this FUBARed Instrument Cluster Repair he is doing in this next video for example. This Guy is performing Damaged and Missing Copper Pad Ray-Trace Jumper Wire Surgery with ultra-thin wire and fine solder to resurrect an absolutely DOA Cluster Logic Board. Not only does he show how this can be accomplished... but he takes the time to display ultra-close up work that will save his customer a Ton of Money since other repair shops had told the customer "No Way...". I seriously doubt there is anyone at GMTN who has not experienced some kind of Instrument Cluster failure over the years... so having the chance to be shown how this gets done at an Atomic level... is a pretty good reason to want to join his Channel. This video is an Education in and of itself with how fine grained his instructions and demonstrated techniques are... with yet another "Guest Appearance" of his "GYMKO" Tech2 Hand Held Scanner to show that once finished ...The Proof of his Work really is in The Solder Pudding:

 
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MRRSM

MRRSM

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#5
I'm still very curious about how the VOP managed to get the GM Instrument Cluster 24 Wire Delco Connector... feeding data through a common Female DLC Port so the "GYMKO" Tech2 Hand Held Scanner can communicate well enough to command individual Sweep Hand Dials and run other specific Cluster Panel Diagnostics. To that end... I have researched the information that shows the graphic and textual images and Pin-Outs Diagrams for the Delco 24 Pin Instrument Cluster Connector...and the OEM Common Female DLC Port Interface with Wire and Pin Layouts as well. All that remains is for someone very astute to figure out "Which Wires Go Where... What They Do When They Get Attached... And Why...", See the attached images for all the graphic details:

NOTE:

A while back... I picked up a Used GM 4.2L LL8 PCM that included the C1,C2 and C3 Connectors. Upon arrival... I noticed that these Item(s) were sooted up pretty bad and smelled like Burnt Pine Logs... so I am guessing that this device came out of a vehicle that was abandoned in a Forest Fire somewhere and this would explain why the whole apparatus only cost me $20.00 with Free S&H. THIS PCM will be my "Guinea Pig" for Testing this GM PCM P-10-C1,C2,C3 Connector(s)-to-OBD2 Female Port Connector Harness so I can use the 12 VDC Power feeding into the DLC Connector from the "GYMKO" Tech2 Scanner's Power Supply to wake the damned thing up and determine if this arrangement allows them both to enjoy Bi-Directional Communication. If this Harness works and the "GYMKO" Bench Test of a PCM idea pans out... I'll Document the Components, the Wiring and the Assembly Procedures and take some images of the "GYMKO" Blue Screen Reads of it performing... and perhaps even shoot a video of it in action. I've ordered all of the Connectors and a Complete AWG Quality Set of Color Coded Automotive All Copper Wiring to use for this Harness Build... Nothing Ventured... Nothing Gained... Right? :>)
 

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MRRSM

MRRSM

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#7
If you have a “GYMKO” Tech2 or a Laptop equipped with a USB to OBD2 Cable and whatever flavor of Scanning-Programming you favor … For you folks who own GM Vehicles equipped with either the GEN III or GEN IV V8 Engines instead of the GM 4.2L LL8 I-6… some of this harness equipment can allow you to fairly easily do 12 VDC powered PCM Bench Diagnostics and Custom Bench Top PCM FLASHING with some well explained and easy to understand designs created to work with the “411” Style PCMs with BLUE and RED 80 Pin Connectors.

Now… If I can only figure out how to do this for the GM 4.2L LL8 PCMs via their P10 Style C1, C2 & C3 Connectors:

https://www.lsenginediy.com/tuning-software-equipment/
http://www.gmtruckcentral.com/articles/2014/Bench-harness/bench-harness.html
http://www.gmtruckcentral.com/articles/12200411.html

Custom LSX Bench Tester Wire Harness Builds:

http://www.superchevy.com/how-to/engines-drivetrain/1401-custom-lsx-wiring-harness-build/

THIS is how expensive these things can get when somebody else having the parts, the knowledge and the wiring schematic… puts these parts together… Just like THAT and sells these for a small fortune:

https://vcmstore.com.au/products/ls1-bench-programming-harness

And likewise… from PAINLESS has a similar device ...for somewhat less money:

https://autoplicity.com/92171-painl..._medium=CSE&utm_campaign=ShoppingComNOFITMENT

And from another GM Forum… another HOW-TO on the work the same project with some variations on the build and with an Excellent Wire to Component(s) Builder Schematic for reference:

https://www.gmforum.com/tuner-139/making-offboard-tuning-278839/

Oh… and for the sake of a little entertainment… Here is an interesting Youtube Video of a “Poor Man’s GM LS Engine Rebuild Break-In Stand” with some surprising and clever ideas displayed on manipulating only “Two Wires” on the OEM Factory Engine Harness to get it to work! The Very Cool VOP (Video Original Poster) Strongly urges Caution and Care while doing this as there is some very obvious danger involved while working with this set up… So Beware the The Ill-Informed about what unrestrained “Engine Torque” is really capable of for those with no Common Sense about Safety:

 
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MRRSM

MRRSM

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#8
The two OBD2 Port-with-Wire-Connectors and The WireGarage.com Kit containing 120 Feet of AWG (American Wire Gauge) 18 Full Copper Automotive Wire Bundle made up of (12) 10 Foot Length Segments and with (12) Unique Colors that I ordered a few days ago arrived this evening from Amazon. As with everything else that I work on... I hate leaving anything to chance where using the right materials in the proper application is concerned. Using Quality Products along with clear thinking and a decent skill-set are the only ways to work on such projects.

If you intend on modifying or repairing ANY under-hood or critical wiring either on your engines (and components)... or inside of your vehicles... THIS is the stuff you will want to work with and avoid easily overheating sub-standard wiring and inviting fire hazards. I took a few images of these items that will soon find a home in a harness that will solve the inter-connectivity problems of bi-directional communication between my "GYMKO" Tech2 Scanner ..and the GM 4.2L P-10 Style PCM via the C1,C2 & C3 Connectors in a Bench-Top setting. All that remains now is to dope out a proper Wiring Schematic and carefully assemble and test out this "The GYMKO PCM Bench Harness":

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MRRSM

MRRSM

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#10
Okay... I just got finished Mapping out the Wire Connections between The GM 4.2L P-10 Style PCM using ONLY Connectors C1 Blue and C3 NAT to make all of the necessary Tie Ins. Connector C3 (GRAY) is NOT employed in this Harness. I marked these wire connection positions on the PCM Connector Print Outs and Highlighted them in Yellow Marker for others to use. The notations over the involved Pins showing the locations of each Individual Pin being selected from within the Pin Matrix using a with a line ending as a Tiny Black Dot resting directly over them and then writing out the information about each of the corresponding connections made between each Connector and The 16 Pin OBD2 (female) PORT out in the Margins of each page.

I've been up all night working on this ... so it might take me a day or so to mock up all of the Hardware Connectors and related Mapped Wiring to create a durable and useful GYMKO Bench Harness... but there is certainly nothing preventing anyone else possessing these Connectors and the proper AWG Wire Segments from making their own version of the Harness from the attached set of images.

If this comes to pass... and the User has a "GYMKO" Hand Held Scanner... as long as the Tech2 AC/DC Power Supply is Fed Into the VCI-OBD2 Tech2 Cable Adapter right at the Power Connection point where the OBD2 Male component plugs into the Female OBD2 Harness Connector... rather than via the Power Connection Port Located on the Bottom Right Hand Side of The "GYMKO" Tech2 Scanner... then there should ample and sufficient 12 VDC present to Power UP the GM 4.2L P-10 PCM ...AND ALSO.... Power up the "GYMKO" Scanner as well... and then it should NOT be necessary to use an External 12 VDC Power Supply to wake up the PCM during the Diagnostic Procedures and Keep It Running. I emphasize that if the 12 VDC Power Plug is directed instead through the bottom of the "GYMKO" Hand Held Scanner... then this procedure WILL NOT WORK. It follows that if you are using any other type of Scanner or Laptop... Then the GYMKO Harness will need to be re-worked to include the necessary FUSED (+) Positive and (-) Negative Power Lead Connections and unfortunately... at the moment... the attached Diagrams DO NOT INCLUDE THOSE MAPPED POWER CONNECTIONS:

TECH2POWERMETHODS.jpg


C2WHITETOOBD2.jpg C1BLUETOOBD2.jpg BESTGM42LPCMTOOBD2PINOUTS.jpg OBD2TOC1BLUEANDC2NAT.jpg
 
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MRRSM

MRRSM

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#11
Okay... This is a Perfect Point to Pause in this Thread for a Better Clarification... It is NOT Absolutely Necessary to have the C1, C2 & C3 PCM Electrical Connectors to Make This Set-Up Work! You would simply have to Create Individual Pin Connectors that need to be carefully Soldered onto the proper contact ends of the GYMKO Bench Test Wiring from Harness leading from The OBD2-Female Port Wires over to the PCM. Of course, each Wire Contact would require a Taped On Set of Simple Instructions as to Which of the Three PCM Pin Matrix (BLUE,GRAY or NAT (TAN) gets these wires attached firmly... by Carefully plugging them in... one at a time so as not to damage the Pins receptacles inside of the PCM. (I can't tell you at this very moment whether or not these Individual Connectors would have to be either Male or Female... as I don't happen to have the three of them removed from the "Guinea Pig PCM" ...Yet... But... please read on for more details).

This morning... I brought out the Used and Well-Worn Donor GM 4.2L PCM ...which I will affectionately refer to henceforth as "Old Smokey" because it very much appears that the Trailblazer of Envoy this PCM came from ...Died an Ignominious Death at the Hands of a Raging Forest Fire...and the resultant Sooty exterior and Pungent Burnt Pine Odor is a dead evidential giveaway that this is what happened. Nonetheless... it suits our purposes in its "After-Life" as a Test Bed for The Gymko Bench Test Harness. I took some snaps of the Damned Thing just before I discovered that it was impossible to remove the Rusted On Three Fasteners that seem to have an odd 6.5MM Hex Bolt Head Dimension and I was reluctant to bear down too much without first soaking the Lil Devils down with a healthy dose of CRC "Freeze;Off" Rust Busting Stuff. I'll give them some time to mend their rusty ways before I venture out into the garage and try to unwind them... so that We can get on with our Autopsy of "Old Smokey" :>)

DSC01275.jpg DSC01276.jpg DSC01277.jpg DSC01279.jpg DSC01278.jpg
 
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MRRSM

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#12
Okay… I finally got the rusted on Trapped Fasteners for all three PCM Connectors to ‘relax and unwind’ and allow me to pull all three. I decided since the suggested Schematic and Diagram designated that only the BLUE and the NAT (TAN… but it looks WHITE to me…) Connectors are involved in the making of the GMYKO Bench Harness… that I would concentrate my efforts into taking only the GRAY One apart to determine how much of a hassle it will be to de-construct the other two ...then ‘de-pin’ the both of them and build those two right back up with only the (4 Pins) necessary cross-connected wires that feed back into the back side of the OBD2 Port portion of this Harness. It became necessary to use a Center Punch and Plastic Mallet to drift out the Lockdown Trapped Fastener, ruining the Spring Steel Keeper Washer but allowing further disassembly afterwards.

These things are a lot more complicated than you might think they would be... on first blush… But actually they behave like a Chinese Puzzle Box… the more you take them apart… the more you find left that you have to take apart! In any case… I wanted to faithfully record this procedure and I wound up needing 42 digital images to get all of the gory details… ergo… you can view this work over on my Photobucket via this link:

http://s557.photobucket.com/user/60...ENGINEREPAIR/GM42LPCMCONNECTORS?sort=2&page=1

One of the images shows how I selected out one, thicker Orange Colored Wire that obviously is intended for carrying the Full 12 VDC versus the other wires which appear to a lot less ‘chubby’ and in all likelihood only have to carry 5 VDC for signaling and communication with all point and contacts within the Vehicle. The other significant observance here is how incredibly robust and “gummy” the Outer Connector Seal and the Inner Wire Matrix Guide Seal are… sort of an OD Green and apparently… virtually indestructible. The individual Wire Female Post Connectors also look very sturdy… nonetheless… being as tiny as they are… I’d suggest using a pair of Needle Nose Pliers when installing them onto and over the (4) requisite Male Pins once they are connected to the right source wires coming from the OBD2 Port.

When next I can attempt that portion… I will use some Black Heat Shrink Insulators and make them all as durable and protected from short circuiting as possible. I will attach just two images to this post; one that shows a‘straight down the barrel of the gun’ view of these blocks of Pins and the other is of a Single Female Pin Connector and attached Wire. I stress that it makes perfect sense to use just these individual Pin-Wires rather than attempting to De-engineer the brilliance Delphi brings to their manufacture of such lasting and functional components… and more or less, it allows me to take the EZ Way Out and still hope for absolute success when building the GYMKO Bench Test Harness in this abbreviated way. This may be one of those rare instance where my doing it thusly will make the doing of this job for anyone else interested in attempting it ...just as easy:

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