CEL triggers only while cruising

[Schurkey]

Also, i tried measuring the voltage from the HARNESS to Ground and it reads 1.48V. According to the flowchart either an open ground or i need a new ECM... i checked the ground and its good.
I haven't seen any threads on this site end with replacing the ECM, so you can see my skepticism.

Is your voltmeter accurate? Are you on the right scale? At least 10K ohms input impedance? (More than 10K is OK, even preferable.)

Here is the AllData diagnostic flowchart for DTC 13.
I've followed the chart and i end at "OPEN CKT 413, FAULTY ECM CONNECTION OR ECM over 0.6v [1.5v]"

There must be some reason the ECM is sending 1.5v to the O2 sensor, or at least it must be some clue for whats going on.

You must be registered for see images attach

1. That chart is for a carbureted Spectrum. You have a fuel-injected V-8 pickup truck. No promises that the chart is accurate for your vehicle. Get a REAL service manual for YOUR vehicle.

2. HOW are you checking the voltage? Chart says to disconnect the O2 sensor, jumper the harness side to ground, start engine, and look at the O2 voltage on a scan tool. Should be less than 0.2 volts. IS IT?

What is the scan tool showing for O2 voltage with the sensor connected normally as you drive?

EGR has been replaced with new factory-grade parts.

Maybe you have a positive-backpressure EGR valve, and with no catalyst, it doesn't have any backpressure to make it work like it was engineered to.

 

[Madison Mehlhose]

Is your voltmeter accurate? Are you on the right scale? At least 10K ohms input impedance? (More than 10K is OK, even preferable.)

1. That chart is for a carbureted Spectrum. You have a fuel-injected V-8 pickup truck. No promises that the chart is accurate for your vehicle. Get a REAL service manual for YOUR vehicle.

2. HOW are you checking the voltage? Chart says to disconnect the O2 sensor, jumper the harness side to ground, start engine, and look at the O2 voltage on a scan tool. Should be less than 0.2 volts. IS IT?

What is the scan tool showing for O2 voltage with the sensor connected normally as you drive?


Maybe you have a positive-backpressure EGR valve, and with no catalyst, it doesn't have any backpressure to make it work like it was engineered to.

I verified my voltage measurements with another DVM and its accurate.
See attached images for resistance.

I re-checked the procedure of jumping the O2 harness to ground and starting and reading the voltage the scan data shows, no surprise, ~0.45v. It shows 0.4 to 0.5v almost all the time.

I uploaded my O2 data for a short drive around town.

The EGR part i have in there is what GM recommends for my vehicle. The only options for replacement at any parts store is the same type.

Can anyone attest to what kind of EGR system my truck is using?

https://imgur.com/a/WEECDZl

 

[Madison Mehlhose]

View media item 31714View media item 31713

I bought the actual service manual for my truck. I think it has the information i need. Just a very small note that wasn't on the other images i was seeing online.

I did not see the note on the bottom left of the code description saying "...if CKT 413 is open, the ECM voltage on CKT 412 will be over 0.6 volt."
Also, i had been checking for ground on circuit A12, which is the main ECM ground and not D6, the O2 sensor ground, how could i not know that. *Rolls eyes*

I am going to check ground on D6 and if that is not it then the truck is up for sale.

 

[Madison Mehlhose]

https://imgur.com/pqiZgU4
https://imgur.com/zor7Pc8

 

[Madison Mehlhose]

SOLVED!!!

Yup that did it. Oxygen sensor is reading great now. Only issue now is i'm getting some spark knock - but its probably just from fuel trims that are way out of wack. I hope the computer will work it out soon!

Moral of the story:

Get an exact service manual for your truck
Check your grounds

Thanks everyone for the help!!

 

[Schurkey]

As long as it all works and runs OK, and the fuel trims stabilize as the computer re-learns...you're set.

I still have some concerns about spark knock and the EGR valve/lack of catalyst back-pressure. The obvious solution in that case would be to slap an aftermarket catalyst back in place.

 

[Madison Mehlhose]

Is there something you would recommend? It’s true dual setup.

 

[sgmbald1]

So is D6 grounded near the

 

[sgmbald1]

So I have been fighting the same issue for a while also and I know that it is related to the O2 sensor and I also did not know about checking D6 ground. My question is where does D6 ground at. Is it on the intake manifold or is it inside the cab near the ECM?

 

[Madison Mehlhose]

So I have been fighting the same issue for a while also and I know that it is related to the O2 sensor and I also did not know about checking D6 ground. My question is where does D6 ground at. Is it on the intake manifold or is it inside the cab near the ECM?

Mine was tucked into the wiring harness shield thingy and cut short with no connector or anything. I attached it to the intake manifold ground near the temp sensor.