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@stef_204
<snippity, snip>

(Another thing I have is that the voltage gauge is busted and for 6 months went all the way past the max voltage and got stuck there; I could see a spike using an ODB app but it would come back in range to normal values so I didn't worry about it. Strangely, possibly because of weather change, or something, it has come back in range now and just fluctuates within an acceptable range now, but it's definitely busted. The point here is: might it be sending the wrong values to the ECU thus screwing things up even more with incorrect values? I should think not.)

A lot of troubles there are from a bad stepper motor.​

I'll try to find the same values you posted with the pics and see if anything looks weird. So far, I haven't noticed anything but will take more time to do it.

I'm still thinking the next "throw $ at it" step would be the actual TPS under the hood but it'd be good to "know before you go" as JoeMontana has said.

Do you have the ability (read: the tools) to check the command-and-response of the TPS?
 

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Discussion Starter · #42 ·
A lot of troubles there are from a bad stepper motor.
Yes, I have read that and would need to test it. If you know how I can test it, please let me know.

Do you have the ability (read: the tools) to check the command-and-response of the TPS?
I don't think so. I would likely need something more sophisticated than just an OBD2 phone app?

Incidentally, the CEL is back on most of the time now; and the abrupt shift as well. This abrupt/violent shift occurred yesterday (although not as strong) while shifting from Reverse to 1st (Drive). First time ever between those 2. It seems like it gets "delayed" or lags; and then, realizes it's in the wrong gear and all of a sudden, shifts into the chosen gear.

Let me ask again, what could be causing that (intermittently--most of the time it is fine; but this occurs frequently enough to be of concern)?
 

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Discussion Starter · #43 ·
I ran a new diagnostics test with one of the OBD apps today on a short ride and this is what I got as Error Codes:

Car Scanner ELM OBD2
DTC report
Selected brand: Saab
VIN: *

============1==============
P0121
Raw code: 0121
ECU: Engine control unit
Status: Confirmed
OBDII: Throttle position (TP) switch A/accelerator pedal position (APP) switch A - range/performance problem

============2==============
P0171
Raw code: 0171
ECU: Engine control unit
Status: Confirmed
OBDII: System too lean, bank 1

============3==============
P0174
Raw code: 0174
ECU: Engine control unit
Status: Confirmed
OBDII: System too lean, bank 2

============4==============
P2119
Raw code: 2119
ECU: Engine control unit
Status: GM failure record
OBDII: Throttle actuator control (TAC), throttle valve - range/performance problem
General Electrical Failures [0x00]
============5==============
P0121
Raw code: 0121
ECU: Engine control unit
Status: DTC supported by calibration, Test failed since DTC cleared, History DTC, Current DTC since power up, Warning Indicator Requested
OBDII: Throttle position (TP) switch A/accelerator pedal position (APP) switch A - range/performance problem
General Electrical Failures [0x00]
============6==============
P0171
Raw code: 0171
ECU: Engine control unit
Status: DTC supported by calibration, Test failed since DTC cleared, History DTC
OBDII: System too lean, bank 1
General Electrical Failures [0x00]
============7==============
P0174
Raw code: 0174
ECU: Engine control unit
Status: DTC supported by calibration, Test failed since DTC cleared, History DTC
OBDII: System too lean, bank 2
General Electrical Failures [0x00]
============8==============
P2119
Raw code: 2119
ECU: Engine control unit
Status: DTC supported by calibration, Test failed since DTC cleared, History DTC
OBDII: Throttle actuator control (TAC), throttle valve - range/performance problem
General Electrical Failures [0x00]

This is a different app, more detailed than the first one and it seems to show up an additional code, 2119.

Not sure if this is useful.

I could not find any values which looked weird while running the car, using the app. I checked pedal position, etc., it all seemed to respond normally (although I'm no expert.)

I did notice this, though:

Font Slope Screenshot Technology Electronic device
 

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To be honest up front - I didn't read this entire thread.

However, according to your screenshot you definately have an O2 sensor issue which could cause other issues with the truck.
First thing I would do is crawl under the truck and verify that the 02 sensors are there and connected with no burned wires all the way up to the main wiring harness near the firewall - (far too common issue on any truck / car.)

Have you also checked the MAF sensor? Might be worth time to clean it with the correct MAF cleaner (NOT brake cleaner!) and check the wires for damage.

I will be first to admit intermittent electrical issues are a giant PITA to isolate and properly correct.

Good luck!
 

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Okay .... now we've got some information ...... and for you fortunate people out there - and you know who you are ---- there's a small amount of Logic Probe class here today!

Hand tool Automotive tire Cable Auto part Wire


.... and just $9.99 at Harbor Fright! Yippee!


I digress ....

The PASS - FAIL indications you posted mean some devices haven't been tested yet ... it's just something that indicates the previously old codes were erased not too long ago and the values from some of the devices haven't yet been been quantified.

It's normal and will self resolve after the baseline thermal cycles (ambient cold-then-operating hot events) have been reached.

SOME OBD Drive Cycles need actual mileage as their qualification metric to be tested and turn them GREEN.

When I was inspecting emissions for California, and that the CEL was OFF, yet upon scanning I would see some OBD Readiness Monitors .... (the same as OBD Drive Cycles then, but may not be the same now) .... had not occurred, therefore the test was an ABORT FAILURE and the customer had to return after they had reset.

So ... like the last person said ... confirm the wiring to the Oxygen Sensors USING A DVM or a LOGIC PROBE to confirm the 12V heater power is there when cold, the GROUND is good and the sensor's generated digital Voltage is there too.

You might not get the sensor to talk while the engine is running ... that would confirm the sensor is bad IF all the other metrics are within normal limits (WNL).

I have little experience with your specific vintage vehicle and model... at the moment I'm stuck in a time warp somewhere below 2006 or so, but I'm advancing daily.
I say this because I don't know for sure the placement of your Oxygen Sensors .. and I'm ASSUMING you have a 4.1L Inline 6 here .......​
But if you have a V-configured engine, ignore most of the following or you're gonna be confused .....​
Bank 1 is always fairly near to- and right after- the exhaust header/collector ...​
Bank 2 may be after the Cat, to confirm that the Cat is correctly operating.​
If there's a Bank 3, then #2 moves up to immediately in front of the Cat and #3 becomes the After Cat sensor.​
Now you can stop ignoring and restart paying attention.....​
Here's a pix of a typical Oxygen sensor in a representative drawing showing the 4 wires with which you need to be conversant:​
Product Rectangle Font Parallel Number

Color codes on the wires* will depend on placement of the sensor - B1, B2, B3, B4, etc., and then there's other POSITION Codes --> S1, S2, S3, S4 etc ... and they may be enumerated like this:​
B1S1, B2S1, B1S2, B2S2, and it goes on and on when you get to the Eurobox vehicles.​
Temporarily ignore all that falderal for now.​
.... but FIRST you need to find the two wires that are the same color as they will logically be the HEATER +12V & -12V
.... the heater POSITIVE wire showing RED on your Logic Probe.​
.... and the heater GROUND will light up GREEN on your Logic Probe.
FUN FACT ---> there are 2, 3, and 4 wire sensors --- and by now there may even be more wires than that.​
* wire colors can be many and these are only representative of common colors, but on some vehicles there may be pink, yellow, blue, green, with or without colored tracers and varying shades of each - so be careful and make sure you know EXACTLY the unit you need to buy and unfortunately you have to trust the guy behind the counter to get the right one.
ALWAYS supply the YMM and VIN to get the right sensors.
REMEMBER that a Logic Probe can test all the wires in your vehicle - including the computers, motors, sensors and ALL primary wires plus their effective grounds too - well, except for the spark plugs secondary voltage!​
A Logic Probe doesn't test the amount of Voltage - just the existence of power or ground. At that - it is a very powerful diagnostic tool that you should have in your toolbox.​
Back to the Oxygen Sensor wires ------>​
√ One of the two oddball and non matching wires will be the generated output signal from the sensor as it creates a digital voltage because of it's interaction with any oxygen molecules left in the exhaust.​
√ You can probe both of these with your Logic Probe because it cannot damage the sensor in any way, but the generated signal from the Oxygen Sensor may or may not create a sufficient signal that will trip the LEDs in a Logic Probe to light it up.​
√ The final and 4th wire will be the GROUND (Earth) and will light up GREEN on your Logic Probe.​
√ Resolving the Throttle Position Motor problem would best be done with an oscilloscope ... but a DVM with a Frequency Test Plotting ability would suffice.​
Rectangle Font Number Brand Logo
← a scope pattern ....​
◇ Watching square wave digital 0/1 signals expand/contract would be okay in detecting that such a waveform exists, but at the same time would be kinda inaccurate with a non-plotting DVM.​
SIDEBAR QUESTION-----> is there a K&N air filter on this engine?​
Does it have a Cold Air Pack?​
FUN FACT ---> The TAC is most likely a bad player here but I certainly don't condemn it until I see the numbers.​
And another thing:​
Your Voltage Indicator Meter (aka: stepper motor) in the cluster has no actual test other than if you know the indicated Voltage is 'way wacky ... and you have tested the Voltage AT the B+ lugs (with a known-good DVM) on the fuse-relay panel and that Voltage is correct ... the stepper is THEN very suspect.​
Why test at the lugs on the panel? Because that's where most of the 12V base-reference signals are acquired for the computers.​
Then ... going farther ...using a meter test the voltage on both sides of each fuse in the circuit you suspect.​
If you use a Logic Probe here on a selected fuse, one side should be B+ 12V RED and the other side should be too!​
But if one side tests 12V B+ RED and the other side tests GREEN --- then the fuse is bad.​
√ I test them all, but YRMV. .​
NOTE: There will be a very minor drop in voltage between the fuse test points on the same fuse shown using a decently good meter --- and that's normal -- and it's also a test depending on the Amperage value for each fuse that is, which now becomes another testing arrow in your quiver.​
All fuses have a resistance value (Ω) that is readable - and this value represents not only the presence of power, but the consumption of it because there cannot be resistance without electrical flow.​
FTR ---> a GOOD DVM won't load the circuit sufficiently to change the flow of power - it only records it; it doesn't modify it!​
I hope I haven't confused you ... it is easy to get lost in electrical testing and things start swirling around in your head .... just write down what you see during your testing and try to build a logic tree.​
BTW .... testing a suspect circuit almost always starts at the device that is assumed to be bad or malfunctioning .... and working back to its power source.​
THEN when you find the fault, you can form your game plan ...​
1. Replace it ...​
2. Repair it ...​
3. Restore it ...​
4. Bypass it ...​
..... but don't do #4.​
PS: I proofread this article and I think it's accurate --- but I know I will get told if it's not. .​
PPS: I said Logic Probe 10 times, including here.​
 

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Okay .... now we've got some information ......

The PASS - FAIL indications mean some devices haven't been tested yet ... it's just something that indicates the previous codes were erased not too long ago and the values from some of the devices haven't yet been been quantified.

It's normal and will self resolve after the baseline thermal cycles (ambient cold-then-operating hot events) have been reached.

SOME OBD Drive Cycles need actual mileage as their qualification metric to be tested and turne them GREEN.

When I was inspecting emissions for California, and that the CEL was OFF, yet upon scanning I would see some OBD Readiness Monitors (the same as drive cycles then, but may not be the same now) had not occurred ..... therefore the test was an ABORT FAILURE and the customer had to return after they had reset.

So ... like the last person said ... confirm the wiring to the Oxygen Sensors USING A DVM or a LOGIC PROBE to confirm the 12V heater power is there when cold, the GROUND is good and the 5V reference voltage is there too.

You might not get the sensor to talk while the engine is running ... that would confirm the sensor is bad IF all the other metrics are within normal limits (WNL).

I have little experience with your vintage vehicle ... at the moment I'm stuck in a time warp somewhere around 2006 or so, but I'm advancing daily.
I say this because I don't know for sure the placement of your Oxygen Sensors .. and ASSUMING you have a 4.1L Inline 6 here ....... if you have a V-configured engine, ignore the following or you're gonna be confused .....​
Bank 1 is always fairly near and right after the exhaust collector ...​
Bank 2 may be after the Cat, confirming the Cat is correctly operating.​
If there's a Bank 3, then #2 moves up to immediately in front of the Cat and #3 becomes the After Cat sensor.​
Resolving the Throttle Position Motor problem would best be done with an oscilloscope ... but a DVM with a Frequency Test ability would suffice.​
◇ Watching square wave digital 0/1 signals expand/contract would be okay in detecting that such a waveform exists, but at the same time would be kinda inaccurate.​
SIDEBAR -----> is there a K&N filter on this engine? Does it have a Cold Air Pack?​
FUN FACT ---> The TAC is most likely a bad player here but I certainly don't condemn it until I see the numbers.​
And another thing:​
The Voltage meter (stepper motor) in the cluster has no actual test other than if you know the indicated Voltage is 'way wacky ... and you have tested the Voltage AT the B+ lugs (with a known-good DVM) on the fuse-relay panel and that Voltage is correct ... the stepper is THEN very suspect.​
Why test at the lugs on the panel? Because that's where most of the 12V base-reference signals are acquired for the computers.​
Then ... going farther ... test the voltage on both sides of each fuse in the circuit you suspect.​
√ I test them all, but YRMV. .​
NOTE: There will be a very minor drop in voltage between the fuse test points on the same fuse --- and that's normal -- and it's also a test depending on the Amperage value for each fuse that is, which now becomes another testing arrow in your quiver.​
I hope I haven't confused you ... it is easy to get lost in electrical testing and things start swirling around in your head .... just write down what you see and try to build a logic tree.​
BTW .... testing a suspect circuit almost always starts at the device that is assumed to be bad or malfunctioning .... and working back to its power source.​
THEN when you find the fault, you can form your game plan ...​
1. Replace it ...​
2. Repair it ...​
3. Bypass it ...​
..... but don't do #3.​
.​
TBSS has a LS2 Gen 4 V8 from the factory.
 
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Discussion Starter · #49 ·
To be honest up front - I didn't read this entire thread.

However, according to your screenshot you definately have an O2 sensor issue which could cause other issues with the truck.
First thing I would do is crawl under the truck and verify that the 02 sensors are there and connected with no burned wires all the way up to the main wiring harness near the firewall - (far too common issue on any truck / car.)

Have you also checked the MAF sensor? Might be worth time to clean it with the correct MAF cleaner (NOT brake cleaner!) and check the wires for damage.

I will be first to admit intermittent electrical issues are a giant PITA to isolate and properly correct.

Good luck!
I did clean the MAF Sensor with MAF Sensor Cleaner and change the air filter, before posting last comment.
 

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Discussion Starter · #50 · (Edited)
Okay .... now we've got some information ...... and for you fortunate people out there - and you know who you are ---- there's a small amount of Logic Probe class here today!

SNIP
I hope I haven't confused you ... it is easy to get lost in electrical testing and things start swirling around in your head .... just write down what you see during your testing and try to build a logic tree.​
BTW .... testing a suspect circuit almost always starts at the device that is assumed to be bad or malfunctioning .... and working back to its power source.​
THEN when you find the fault, you can form your game plan ...​
1. Replace it ...​
2. Repair it ...​
3. Restore it ...​
4. Bypass it ...​
..... but don't do #4.​
PS: I proofread this article and I think it's accurate --- but I know I will get told if it's not. .​
PPS: I said Logic Probe 10 times, including here.​
Thanks!
Let me read and try to digest all of that ;)
And, I have the LH6 5.3 Ltr. V8 (NOT the 6 cylinder 4.2 Ltr.)
I will also run the OBD app again and check if any codes and errors as mentioned above are still there.
 

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The pedal sensor code is still coming up, you said earlier you were under the dash and moving stuff around I would take time and make sure you didn't jiggle something out of place. Is this the original motor? Original ecu? Does it have a tune in it? I have a mail order tune from pcm with the secondary 02 sensors turned off (B1S2 B2S2) and every few months I will get a CEL for rear 02s that I just clear and move on. If your confident moving forward I would suggest buying the service manual. It will give you all test points, procedures, and possible issues. DO NOT buy Chilton or Haynes books they suck and when testing they all say "typical fuel injection system" which would be a theory but not exact application. Get a good DVOM and write everything down so you know where you stand.

Sent from my SM-G991U using Tapatalk
 

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@ Civteck: "DO NOT buy Chilton or Haynes books they suck and when testing they all say "typical fuel injection system" which would be a theory but not exact application. "

Amen.
 
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