Thanks again Captain! I will try hooking a test lamp at the cluster fuse. As the fuse is not blowing, I guess it won't matter what side I tap into for hot; either way the test lamp should go out when the open occurs... That is, If the problem is upstream of the fuse? Correct?

And is there any reason I should use a 12v filament bulb and socket as opposed to an LED?

RE: "... The last place you look??? " I've told the same thing to my kids for years whenever they were looking for something! <LOL> IE. Why look any farther, eh?

 

I've seen the sockets in the fuse panel, and fuses, with issues. Fuse might look good, but still have a problem. There are bus bars in the fuse panel, and they can fail as well. At connectors, you need to inspect each crimp and make sure the insulation is not interfering with the wire to the terminal. With an intermittent problem, you can't leave any stone unturned, take nothing for granted, and assume nothing.

 

OK Captain, I'll keep all that in mind.

 

OK Captain, or anyone who may be following this thread...

1st findings report... Installed test lamp as discussed at #11 CLSTR fuse... Battery voltage showing at fuse and test lamp is lit... SES is still lit but transmission currently operating normally... Cleared all codes to turn off SES light before test drive so as to monitor the test lamp when the problem arises again and the SES lights up and tranny enters limp mode.

After driving a mile or so, SES lights up as expected and tranny temporarily goes into 2nd gear limp mode. However, my Test Lamp stayed lit throughout indicating no loss of voltage at CLSTR fuse #11.

So can I now correctly assume I am looking for an intermittent open in the harness between the fuse and the tranny? If so, where do you suggest I look next? And if not, <BG>, where do you suggest I look next?

Edit: Does this test drive effectively eliminate and rule out the ignition switch as the cause of my problem?

Blazer Tom

 

It rules out the ignition switch and circuit to the CLSTR fuse, that's it. If you had the pilot lamp on the fused side of the fuse, it would eliminate the fuse as a possibility. If the pilot was on the unfused (HOT) side of the fuse, the problem could be the fuse or the connection to the fuse, or anything up to and including the harness in the trans.

 

It rules out the ignition switch and circuit to the CLSTR fuse, that's it. If you had the pilot lamp on the fused side of the fuse, it would eliminate the fuse as a possibility. If the pilot was on the unfused (HOT) side of the fuse, the problem could be the fuse or the connection to the fuse, or anything up to and including the harness in the trans. You'll need to keep moving away from the fuse, toward the trans, until you find the intermittent open circuit.... if that's what's causing the problem We don't know that for certain yet. Testing on the red wire, inside the trans, would tell for certain.

 

Good morning Captain! Knowing that I'd next be heading into the wiring harnesses and connectors, and recognizing the importance of your tag line, I dug up a 3 volume OEM service manual for a '98 blazer. While my current blazer is an '02, I'm pretty sure the basic information contained therein should apply equally to both cars (2nd Generation 1995-2005?).

I spent some time "in the books" last evening and hoping to get a better understanding of the circuits in question and locations of relevant harness connectors and splices. I'm still trying to find a schematic showing the connector on the transmission; which, if I understand the location zoning numbers correctly, should be in the 300-399 range but all the connectors I'm seeing in what I think are the relevant schematics are under the hood (100-199) or at the instrument panel (200-299). I'm still quite confused! Any help on locating the relevant harness connectors for testing individual sections of the harness would be appreciated.

RE: your comments on the test lamp being on the hot side vs the fused side of the CLSTR fuse... While I'm pretty sure I was on the hot side, I think I can rule out a faulty fuse because I've never noticed any loss of functionality in the instrument cluster. Would you agree?

RE: "Testing the red wire inside the trans would tell for certain." Can the red wire inside the trans be tested from the connector on the outside of the transmission?

I look forward to your reply! BT

 

Absolutely.

Unfortunately, no. To test the harness in the trans, the pan needs to be dropped to thoroughly inspect the connector and harness.


In your '98 shop manual, "Volume 3 of 3, page 7-66, shows the schematic for the shift solenoids. The connector in question is "C175" with the pink wire on pin "C" of the connector. Inside the trans, it changes to a red wire.

 

Great! That's encouraging!

Too bad! I think I'll save pulling the pan and testing inside the trans for last!

Yep! In addition to the individual DTC schematics for each of the five codes I'm getting, the transmission controls schematic on 7-66 is what I was referring to. At first I thought C175 had to be the transmission connection; but from what I read in Volume 1, pages 8-302 to 8-307 (How to use schematics), I thought the 175 in Connector C175 indicated a "Truck Zone number" that would place C175 under the hood! Thus my continuing confusion on connector locations...

My plan is to test circuit 1020 for continuity or intermittent opens in each section of harness: Starting from CLSTR Fuse 11 to Connector C203, then from C203 through the Grommet P100 & Splice S113 to Connector C101, then from C101 to C175 at the trans...

Question 1) Does the above plan sound like a valid approach?

Question 2) If the numbers in C203, C101 and C175 do not represent "Truck Zone" locations, as I thought, how can I determine the location of these other connectors C101 and C203?

Question 3) I understand the Color Codes (PNK) and Circuit numbers (1020) in these schematics but what does the "0.35" in "0.35 PNK 1020" indicate? Is this a metric wire size as opposed to an SAE or AWG wire size?

Question 4) Can you confirm that the K4 associated with C203, and the G associated with C101, and the E associated with C175, in the schematics are the actual terminal pin numbers within these multi-pronged connectors?

I do appreciate your help! BT

 

Correction: The pink wire in the transmission connector goes to pin "E", not pin "C" as mentioned in post #18.


Question 1) Great plan. When testing continuity, give the wire and connections a good "wiggle test". You'll need to check the splice right at the fuse connector inside the fuse panel, it's not fun. It's possible that circuit 1020 has a poor connection where it takes off to the trans, and doesn't affect the cluster. Might want to skip this step and come back to it later if necessary, up to you.


Question 2) The component locator is your friend Starting on page 7-68, it gives the locations of connectors, grounds, grommets, splices etc. It also tells you how many cavities are in each connector, so you know basically what you're looking for. If you dig around a bit, it tells you what color the connector is too. ie: page 7-74, right side, tells you the transmission connector is grey, it has 20 pins, and not all pins are used.


Question 3) You're correct, the numbers indicate the metric size of the wire, not AWG.


Question 4) See question 2.