Failed Emissions / No Com

Juan Mobile Technician Montgomery, Illinois Posted   Latest  
Question
Network Communications
2006 Chevrolet Malibu LT 3.5L (8) 4-spd (4T45-E)—1G1ZU53826F208924
Failed Emissions Test

The car has failed emmisions due to no communication at the testing facility. I am able to communicate with three different scanners with all modules in vehicle. This vehicle has a low speed LAN (pin1), Class 2 (pin2), high speed LAN+/- (pin6/14). I plan on to scope each data line and see if the data signals are correct. If I notice anything odd I will start to isolate modules. Also check pin tensions at the DLC. My question is, what data line do emmison test stations connect on? Also is it possible to have a voltage drop/high resistance on a data line that may be affect by emission test station equipment? Thank you and I hope to follow up soon with images of a possible fix

0
Kevin Diagnostician
Poughkeepsie, New York
Kevin
 

Historically, if it were German, I would suggest that an active fault in the abs would allow communication with a scan tool but disallow communication with an emmisions computer. 

+1 Ð Bounty Awarded
Martin Instructor
Burnaby, British Columbia
Martin
 

The Malibu with 3.5L LX9 doesn't use the Class 2 bus, even though it may be there at the DLC. That is reserved for use on the same vehicle when equipped with L61 (2.2L ) and only then for diagnostics and programming. 

The HS LAN at terminals 6 and 14 is used for high speed real time data needs. 

Unlike single wire busses that are not fault tolerant, the dual wire HS GM LAN is fault tolerant, meaning that while there may be a bus issue, data may still be communicated on the parallel leg if a failure occurs on one side. Test the bus as you would for any HS CAN

+2 Ð Bounty Awarded
Juan Mobile Technician
Montgomery, Illinois
Juan
 

Thank you for the advice, I was not aware of a parallel leg failure and it still being able to communicate.

0 Ð Bounty Awarded
Juan Mobile Technician
Montgomery, Illinois
Juan
 

Also how did you know that the 3.5 LX9 doesn't use the Class 2 bus? Id imagine this follows the same on many other vehicles.

0 Ð Bounty Awarded
Martin Instructor
Burnaby, British Columbia
Martin
 

GM SI. It states that Class 2 is only used on the 2.2L L61 application and not the 3.5L LX9. For the 2.2L it is only used for diagnosis and SPS.

0 Ð Bounty Awarded
Robert Diagnostician
Ballston, New York
Robert
 

It will communicate on pins 6/14 high speed lan. Have you tried communicating with the pcm in generic mode with a scan tool?In the past I’ve had some modules fail to communicate on the generic side but function properly on the oe side. Almost always there is a reflash available to rectify that concern. 

+2 Ð Bounty Awarded
Juan Mobile Technician
Montgomery, Illinois
Juan
 

The first scan tool I tried was generic pocket scanner and it communicated fine. Although I have not tried it on my bi-directional scan tools. I am going to be in contact with the dealer today to see if there is a re-flash available.

0 Ð Bounty Awarded
Adrean Diagnostician
Bakersfield, California
Adrean
 

How many emissions computers have you used just one or more ? If one I will try somewhere else 

0 Ð Bounty Awarded
Juan Mobile Technician
Montgomery, Illinois
Juan
 

When I originally had the car last week, I checked for power and grounds at the DLC, communicated with 3 different scan tools. Did a quick check on the data lines to see if there was data being sent. After that I suggested to try a different test lane, considering maybe it was the emission center test equipment. Car failed again on a different test lane.

+1 Ð Bounty Awarded
Bob Mobile Technician
West Chicago, Illinois
Bob
 

Emission testing is done via the global side. Can you communicate using your scan tools in generic or just manufacture specific?

0 Ð Bounty Awarded
Juan Mobile Technician
Montgomery, Illinois
Juan
 

Yes I was able to communicate with my pocket scanner. I did not try global with my Bi-Directional scanners.

0 Ð Bounty Awarded
Kai Mobile Technician
Chicago, Illinois
Kai
 

The EPA equipment is communicating on HS-CAN, pins 6 and 14. Voltage levels are crucial. A scan tool in your shop, whether OE or AM, is more forgiving than the EPA setup. Scoping the network would be a good start.

+2 Ð Bounty Awarded
Bob Mobile Technician
West Chicago, Illinois
Bob
 

Have you drag tested the pins?

0 Ð Bounty Awarded
Juan Mobile Technician
Montgomery, Illinois
Juan
 

Didn't have a chance to get to the car until tonight. I first connected my pocket scanner in and it did not communicate. Scoped the CAN +/- through a B.O.B. CAN + was not right as you can see in the attached image. First I drag tested the dlc, it was fine. Dissconted the brake module first then the power steering module, no change in signal and the signal looked good at both connectors. Bcm was the next easiest, I had to unplug the connector to access the wires, there was a lot of dyelectric grease in the connector as you can see in the attached image. Once I plugged it back in the CAN + came back. I dragged tested the pins and the CAN + going into the BCM was bad.

I'm assuming this was an issue before due to the dyelectric grease. Regardles I'm happy, thank you every one for the all the advice.

+3 Ð Bounty Awarded
Juan Mobile Technician
Montgomery, Illinois
Juan
 

Screen shot from the scanner

0 Ð Bounty Awarded
James Technician
Plant City, Florida
James
 

The dielectric grease is part of a recall for brake lamps staying on.

+2 Ð Bounty Awarded