NEED HELP Unknown Driver and No Start

[TJBaker57]

continuity line communication pcm canle dark green. It's ok

This refers to post #203

I continue to review all of this thread amd look for possible answers. In this picture, testing continuity of dark green PCM serial data wire, what is the reading on the meter? Does that read 10 ohms? Should this not read at or very close to zero ohms?

Does anyone know what would be the threshold of resistance reading on a class 2 serial data line before the signal might be attenuated enough to cause a lack of communication?

 

[budwich]

I don't know the actual value but I don't think "10" anything is correct for basically a wire run. Having said that, the OP is using the "beep" mode which isn't a very good resistance measurement AND you don't know how much his "test lead setup" is by itself... some baseline measurements are needed there in. I think that you have pointed out a lot of "not sure how you did this" stuff for the OP to double check especially around pins.

 

[Mramses]

This refers to post #203

I continue to review all of this thread amd look for possible answers. In this picture, testing continuity of dark green PCM serial data wire, what is the reading on the meter? Does that read 10 ohms? Should this not read at or very close to zero ohms?

Does anyone know what would be the threshold of resistance reading on a class 2 serial data line before the signal might be attenuated enough to cause a lack of communication?

This refers to post #203

I continue to review all of this thread amd look for possible answers. In this picture, testing continuity of dark green PCM serial data wire, what is the reading on the meter? Does that read 10 ohms? Should this not read at or very close to zero ohms?

Does anyone know what would be the threshold of resistance reading on a class 2 serial data line before the signal might be attenuated enough to cause a lack of communication?

 

[Mramses]

Now what should I check friends?
I check again the resistance from c1 59 to sp205 dark green wire.
and the resistance from c1 58 to f12 c2 bcm?

 

[Mramses]

I made a cable with ties of more than 4 linear meters long and it has a resistance of 1.8 ohm

 

[Mramses]

resistance measurement in this order
c1 59 to sp205 dark green cable
c1 58 to c2 f14 bcm yellow cable
sp205 a c1 b1 bcm
all values do not exceed 2 ohms

 

[TJBaker57]

Now what should I check friends?

Have you taken readings on the PCM, C1 pin 59 to PCM ground, and C1, pin 58 to PCM ground? On my truck PCM the readings are:

C1, pin 59 to PCM ground = 4.66k
C1, pin 58 to PCM ground = 1.2k

 

[Mramses]

Have you taken readings on the PCM, C1 pin 59 to PCM ground, and C1, pin 58 to PCM ground? On my truck PCM the readings are:

C1, pin 59 to PCM ground = 4.66k
C1, pin 58 to PCM ground = 1.2k

c1 pin 58 to ground c2 pin 65=43.6 kohm
c1 pin 59 to ground c2 pin 65=43.6 kohm

 

[Mramses]

friends could bcm be bad? and cause these problems?
Even with the tester it is not possible to measure fluctuating voltage of the data class2 communication line, the measurement of the voltage + green cable bcm and - cable to ground, there is a voltage fluctuation between 0-3 vdc perp after a few seconds it disappears.
the same is true for the pcm.
But when measuring voltage between + gray cable (cluster) and - to ground, a fixed voltage of 1.19 vdc remains, this voltage does not change at any time, it only drops to 0 when turning the key off

 

[Mramses]

C1 pin 58 PCM to ground pcm=9.56 kohm(20k)
C1 pin 59 pcm to ground pcm=9.56 kohm (20k)


if I change the scale from 20k to 200k they give these values
at 20k gives 9.56 both pin 58 and 59
at 200k gives 43.6 both pin 58 and 59

 

[budwich]

try changing the batteries in the meter. I don't believe that your meter should give different readings on different scales. The scales have more to do with the number of digits available for display. A reading of 10k on the 20k scale will read 10.0 but on a 200k scale will read 10.

 

[TJBaker57]

friends could bcm be bad? and cause these problems?
Even with the tester it is not possible to measure fluctuating voltage of the data class2 communication line, the measurement of the voltage + green cable bcm and - cable to ground, there is a voltage fluctuation between 0-3 vdc perp after a few seconds it disappears.
the same is true for the pcm.
But when measuring voltage between + gray cable (cluster) and - to ground, a fixed voltage of 1.19 vdc remains, this voltage does not change at any time, it only drops to 0 when turning the key off

Was this your truck prior to having the engine work done and did the cluster work OK then?

Is it possible the cluster is bad?

I tested my cluster, splice pack comb removed, key to RUN and read 0.04 to 1.76 VDC. The high readings were directly after turning the key on. It then settled to 0.04 and fairly remained there.

 

[TJBaker57]

try changing the batteries in the meter. I don't believe that your meter should give different readings on different scales. The scales have more to do with the number of digits available for display. A reading of 10k on the 20k scale will read 10.0 but on a 200k scale will read 10.

Oddly, I have a meter that behaves the same on some circuits but not others. I have been puzzling over this. Same circuit seen here. My autoranging meter shows yet another reading!

 

[Mramses]

Was this your truck prior to having the engine work done and did the cluster work OK then?

Is it possible the cluster is bad?

I tested my cluster, splice pack comb removed, key to RUN and read 0.04 to 1.76 VDC. The high readings were directly after turning the key on. It then settled to 0.04 and fairly remained there.

but it is not normal that it measures a fixed voltage of 1.19 vdc. must it be bad?

 

[TJBaker57]

but it is not normal that it measures a fixed voltage of 1.19 vdc. must it be bad?

Was the comb in the splice pack when you measured? And the key in RUN?

 

[Mramses]

without the comb in the sp205 and key in run

 

[TJBaker57]

Have you ever tried to start the truck with no comb in the splice pack sp205? What happens?

 

[budwich]

Oddly, I have a meter that behaves the same on some circuits but not others. I have been puzzling over this. Same circuit seen here. My autoranging meter shows yet another reading!

View attachment 97090View attachment 97091
View attachment 97092

quality of the meter... and possibly some "finger problems" during use... for example, trying to measure resistance in a circuit that is powered. Depending on what powering is in a circuit, it may cause "internal problems" with the bridges that are used to measure the resistance. Of course, a check would be an out of circuit, free standard resistor. You know it can not change value from one range to another.

 

[Mramses]

Have you ever tried to start the truck with no comb in the splice pack sp205? What happens?

Yes, friend, I try start every time I do any of the tests that it indicates. so far nothing different all the same.
Check engine turns on, does not start, doors do not work, windows do not work, hvac does not work and unknown driver

 

[mrrsm]

You have probably already done or tried what is covered in this Video... But Just In Case ...Not Yet...

 

[TJBaker57]

You have probably already done or tried what is covered in this Video... But Just In Case ...Not Yet...

"Unknown Driver" does not by itself cause a no start condition.

 

[TJBaker57]

@Mramses

Did you say you had the App "Car Scanner Pro"??

Car scanner Pro has a terminal screen that allows us to 'talk' to the ELM327 and also the vehicle network. The terminal screen is in the "Setting" menu selection. It does NOT do the commands for you, you must know what to type. Here in this first short clip I connect to the ELM327 and ask it to tell me what protocol it is using to try to connect to the vehicle. For our trucks this must be SAE J1850 VPW. This is not speaking to the vehicle yet. This is only talking with the ELM327. But this is where we begin....

Edit: The video seems to clip off the last screen so here is the final output...

 

[TJBaker57]

@Mramses

Here in this video I use Car Scanner Pro terminal to ping all modules on the vehicle network. This might be able to tell what modules are working on your truck, as long as the network is not prevented from working by a short circuit or a bad module. If you can get some communication established you could maybe determine what modules work and what modules do not.

 

[Mramses]

@Mramses

Here in this video I use Car Scanner Pro terminal to ping all modules on the vehicle network. This might be able to tell what modules are working on your truck, as long as the network is not prevented from working by a short circuit or a bad module. If you can get some communication established you could maybe determine what modules work and what modules do not.

very interesting friend. To do these tests, must the sp205 and sp 306 be connected?
How can you know which command corresponds to which module?

 

[TJBaker57]

very interesting friend. To do these tests, must the sp205 and sp 306 be connected?
How can you know which command corresponds to which module?

You can connect any modules you wish to test. Just jumper them to the purple DLC wire. You can test one at a time or any combination.

But first must confirm the ELM327 device connects with SAE J1850 VPW. If it reads something else then there is another command to switch that to SAE J1850 VPW.

The third byte is the address of the responding module:


10 = PCM
1A = TCCM
29 = EBCM
40 = BCM
58 = Supplemental Restraints
60 = Instrument Panel Cluster
80 = Radio
81 = Amplifier
97 = Onstar
98 = HVAC Module
A0 = Driver Door Module
A1 = Passenger Door Module
A2 = Liftgate
A7 = Rear Seat Audio (+HVAC)

 

[mrrsm]

This Link at ScannerDanner is worth viewing for the Network Diagrams and the Discussion:

2004 Trailblazer fixing an issue caused by an idiot

2004 Trailblazer fixing an issue caused by an idiot

www.scannerdanner.com

 

[budwich]

mramses, you continue to be side tracked. TJbaker57 has posted video that shows you only need the PCM to be working. Doing anything beyond that is a waste of time at this point.

 

[Mramses]

understood friend follow the directions. today I carry out the connection tests mentioned

 

[TJBaker57]

mramses, you continue to be side tracked. TJbaker57 has posted video that shows you only need the PCM to be working. Doing anything beyond that is a waste of time at this point.

If this refers to the tests using the Car Scanner app,,, that is indeed aimed at seeing if the PCM is communicating at some level. My tests using the cluster has one inherent flaw,,, what if the cluster is the issue causing the PCM to cluster comm failure? Mramses has tested powers, grounds, and the serial lines from the PCM. Tested internal resistances of the PCM as well and though I see variances with his readings vs mine we have no official documentation to give guidance on what is the right reading. We know the PCM is functional at some level due to the lighting of the MIL light at key in RUN position plus the fuel pump primes, also a PCM function. Short of swapping in yet another PCM I'm not seeing what else to test on the PCM. Anyone got a suggestion?

@limequat Any insight on testing a PCM to confirm operability?

 

[budwich]

If this refers to the tests using the Car Scanner app,,, that is indeed aimed at seeing if the PCM is communicating at some level. My tests using the cluster has one inherent flaw,,, what if the cluster is the issue causing the PCM to cluster comm failure? Mramses has tested powers, grounds, and the serial lines from the PCM. Tested internal resistances of the PCM as well and though I see variances with his readings vs mine we have no official documentation to give guidance on what is the right reading. We know the PCM is functional at some level due to the lighting of the MIL light at key in RUN position plus the fuel pump primes, also a PCM function. Short of swapping in yet another PCM I'm not seeing what else to test on the PCM. Anyone got a suggestion?

@limequat Any insight on testing a PCM to confirm operability?

I was referring to your post of a video (post 178) showing how a truck runs with the PCM and NO comb pack installed with NO jumpers. Hence, you only need to focus on the PCM and not worry about the other modules. Maybe I misunderstand... in which case I leave. Further, the resistance measurement of this devices can't be all over the place... this is either a meter problem or a device issue. The metering can be check against know resistance. Further, I don't believe the OP actually confirmed proper pins for voltages. Anyway, you will make progress based on the great information that you have provided... it just needs to be conveyed to the other end.

 

[TJBaker57]

referring to your post of a video (post 178) showing how a truck runs with the PCM and NO comb pack installed with NO jumpers

Ah! I see said the blind man!
Agreed. But how do we know the PCM is talking? The PCM must communicate with the BCM or you get no crank. The reason it starts without a comb is because the PCM and BCM are connected by a serial data line (yellow wire) that bypasses the splice pack entirely. So I think an attempt at confirming serial data activity from the PCM is warranted.

Hence, you only need to focus on the PCM and not worry about the other modules. Maybe I misunderstand...

You don't misunderstand, I think we are on the same page, but taking different approaches to the same goal of evaluating the PCM functionality.

resistance measurement of this devices can't be all over the place... this is either a meter problem or a device issue. The metering can be check against know resistance

Also agreed. But I have no known resistances at my end and I have no idea what he has either. I felt I was hitting some limits of my knowledge here and maybe another avenue might yield some results.

don't believe the OP actually confirmed proper pins for voltages.

There is indeed a lot of images to review and some are erroneous measurements for certain. My PCM begins serial data with only pin 20 (hot at all times) and pin 21 (Ign 0, ign sw terminal E, rear fuse 47) powered. In reviewing all the photos yesterday in this thread I 'thought' I found those pins powered in Mramses posts.

 

[Mramses]

Help

 

[TJBaker57]

Help

What are the conditions of this test? Serial data jumpers? Splice comb installed or no?
If yes, then try this again with no comb and no jumpers installed. Edit: This was wrong.... You need at least one jumper from the purple wire to somewhere. Try PCM, try Instrument cluster, try Transfer Case module.

 

[Mramses]

What are the conditions of this test? Serial data jumpers? Splice comb installed or no?
If yes, then try this again with no comb and no jumpers installed. Edit: This was wrong.... You need at least one jumper from the purple wire to somewhere. Try PCM, try Instrument cluster, try Transfer Case module.

good night friends. the test was with the sp205 comb installed

 

[TJBaker57]

good night friends. the test was with the sp205 comb installed

It has the appearance of somethong wrong on the network. Like a bad module. One bad module or a shorted wire can short out the network and then no communication is possible.

We already suspect either PCM or BCM so it may be wise to establish communication with other modules to prove the elm327 works. Remove the comb and try with a jumper from purple wire to some other module or modules. Try the blue & white wire to the rear splice pack, that would give 3 or 4 modules. Key needs to be on.

When the elm replied "searching" this meant it was trying different protocols in an attempt to establish communications. By default from the factory the elm327 is set to try protocols in a set order. We can reset it to use SAE J1850 VPW. Do this by entering in the terminal screen AT SP 2.

 

[Mramses]

jumper purple cable and dark green cable in sp205

 

[Mramses]

jumper purple cable and dark green cable in sp205

 

[Mramses]

jumper purple cable and dark green cable in sp205

 

[Mramses]

all the tests throw me "?"
with comb sp205
as with jumper

 

[TJBaker57]

all the tests throw me "?"
with comb sp205
as with jumper

The command is incorrect. Not "AT 10"

Send this.....

AT SH 6C FE F1
20