Permanent DTC's

Scott Owner California Posted   Latest  
Resolved
Emissions
2010 Cadillac CTS Luxury 3.0L (G LF1) 6-spd (6L45) — 1G6DF8EG9A0107024
P0442 — EVAP System Leak Detected (small leak),
Won't Pass Emission Test

Hi All,

A quick question - a customer brings this vehicle in as he's been unable to pass a smog test. He's had a friend put a purge solenoid on and a gas cap and was told to drive the vehicle. The MIL has been coming on intermittently. He tells me it has a EVAP DTC stored, but isn't sure what the DTC is. When it's dropped off he says the MIL went off about a week ago.

I hook up a Tech 2 and check for DTC's and there were no DTC's stored. I check the I/M System Status and all Readiness Flags have completed and passed testing with the exception of EVAP. I tell the customer I'll take it for a smog test to a shop in this complex and then take a look at the EVAP system, once it passes. He's back pretty quickly and says it failed as there's a P0442 set as a permanent DTC. I'm curious why I don't see this with the factory tooling, but I realize there are no options to see any of the other “Mode xx's” using this tool. I hook up my Snap-on Solus Legend and looked all around and don't see the P0442 stored. I would thought I should have seen this - maybe I'm not looking in the right area. I clicked on the OBD-II/EOBD and also built the vehicle and used the generic functions. I have a cheap Harbor Freight code reader and this showed 0 DTC's as well. I went back to the smog shop and he hooks up a Craftsmen code reader and this shows the P0442 - Permanent.

The question is what do I do, or buy, before wasting anytime/money attempting a smog test? I know what Permanent DTC's are…

The fix for the EVAP is going to be a line that a rodent has gnawed at the canister and the line will be here next week.

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Randy Diagnostician
Colorado
Randy
   

Every scan tool I have that is generic capable reads permanent DTCs including Snap-on. I would expect any up to date tool would do so. I am curious why your does not. In the meantime, there are tons of cheap APP based tools on the net that reads all of generic so for under $50 you can get something for a quick check.

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Dmitriy Analyst
Ontario
Dmitriy
 

This video tip from Snap-On says it applies to Solus Legend: snapon​.​com/Diagnostics/US… Do you have $0A tab on your tool?

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Rolando Diagnostician
Texas
Rolando
   

I would take it to an inspection station and have them scan the codes with the official machine. If the official machine shows no codes but readiness is not complete, this means you just haven't hit the parameters to run the EVAP test. I have had scan tools show me , “false” or no codes before with no lights on, but if I go to an inspection station and ask them to check it with the inspection…

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Dave Diagnostician
California
Dave
 

Hi Scott, after the repair your going to have to have a code reader or scan tool that is capable to look for permanent codes, warm up cycles, and miles after code clear to be able to see if the vehicle is ready for the inspection. Hope this helps.

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Danny Technician
California
Danny
   

Hi Scott! The local garage came by my shop with a Triton D10, and he couldn't find the PDTC. In the Generic OBDII code menu, scroll all the way down, and you should see it. Here's BAR's explanation of PDTCs. bar​.​ca​.​gov/Industry/PDTC The vehicle has to successfully run the monitor for that code to clear the PDTC. It may take a while, but if it's fixed, the consumer could drive the 15/200…

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Matthew Owner/Technician
Oregon
Matthew
 

I think this is where some of us get into trouble with scanners and codes. The OE tool might pick up the code but not show it as it's not applicable since it's a “permanant DTC”? I would have thought it would tho. I have a bunch of scanners, some expensive, some cheap, because there's no one tool does all. I've found a few cheaper tools that I find are too stupid to not know they aren't…

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Keith Engineer
California
Keith
 

Different functional request. A PDTC is called at mode (SID) $0A, whereas Confirmed and Pending at modes (SID) $03 & 07, defined by SAE J1979 respectively. However, aftermarket enhanced and OEM scan tool calls modes (SID) $17, 18 or 19, for KWP/UDS on CAN OEM DTCs.

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Elias Owner/Technician
California
Elias
 

we have an old cheap matco scan tool just for these situations that reads monitors, pending,current and best of all permanent dtc's. FOR SOME REASONS WITH LARGE SCAN TOOLS YOU MAY HAVE TO GO UNDER DIFFERENT SECTION/PROTOCOL section to view the Permanent codes.I would invest in one of those small ones that automatically reads when plugged in.

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Tony Owner/Technician
Missouri
Tony
 

Scott, you've gotten good advice RE: it being a permanent code. It sounds like it has been cleared with a scantool and when looking via normal avenues you are not seeing the mode $0A info on any of your scanners. I would suggest you are not looking in the correct places. Of interest would be where/if it shows on your Tech2 as I haven't run into the issue what with not seeing much GM. What I can…

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Michael Owner/Technician
Texas
Michael
 

Permanent DTC will clear once the PCM determines the fault is fix. Never diagnose a permanent DTC or a vehicle you can't duplicate the DTC.

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Michael Owner/Technician
Texas
Michael
 

I use the purge and seal function to diagnose GM leaks.

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Scott Owner
California
Scott
 

Hi Michael, That's what I do as well. There was obviously a problem as the vacuum decay rate seemed like it would have set a P0455 and not the P0442 set as a PDTC. Initially I didn't think of the vehicle having a PDTC set and I didn't want to do anything and have the MIL illuminated before I looked at the EVAP system. On this one I disconnected the purge solenoid hose and hooked up a smoke…

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Tony Owner/Technician
Missouri
Tony
 

I'm suppose your primary concern wasn't to get it to pass at any cost, but had you considered a reflash to clear the permanent code? I'm genuinely interested in knowing if a GM PCM would clear them all, or not, or if the reflashed PCM would show permanent DTCs for all non-continuous monitors until they had ran/passed.

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Scott Owner
California
Scott
 

Hi Tony, My initial concern(s) were I didn't know what DTC had set, but I had a suspicion it was due to a leak as the customer mentioned the gas cap and purge solenoid had been replaced. I thought, incorrectly, as I found out, that there were no DTC's set and prior to looking at this I would smog test it and then look at the EVAP system. Instead of looking at it and possibly setting a DTC. This…

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Tony Owner/Technician
Missouri
Tony
 

Thanks, I understand all of that. I seem to remember some change mentioned a few years ago that disallowed reflashing the same revision but I thought maybe a Tech2 with tis2whatever would be exempt from that restriction. Now I'm thinking, since you mentioned Tech2win specifically, that one can't connect a Tech2 and reflash anymore. Certainly you still have a Tech2 so you would have tried that…

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Scott Owner
California
Scott
 

Hi Tony, I guess for the sake of curiosity you could try to reprogram the ECM and see if that clears the PDTC's, but with completely different architectures between the various ECM's, what works on one model might not on another vehicle. As far as programming, it doesn't matter what interface you're using, (it does, but not for this discussion) they're all phoning home for the 0's and 1's. The…

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Tony Owner/Technician
Missouri
Tony
 

You misunderstood nothing. I was asking for your experiences and knowledge and you answered my questions to the best of your ability, thank you. I have little experience on GM. I no longer have an active subscription nor an MDI so I still use my Tech2 on anything I can, otherwise it gets a barrage of aftermarket tools to get by for now. As a non-specialist I tell people I can only do so much…

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Geoff Diagnostician
Hawaii
Geoff
 

"I'm thinking of 2007 LS engines that in order to relearn the idle I have to program the ECM as the Reset Idle function does not work." Scott, Is this the car that the TechLink article says to "build" it, as a different year (in Tech2) and then the function works?

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Scott Owner
California
Scott
 

Hi Geoff, I haven't had much luck in using a different year as I believe this has to do with on 2007 there's not a PID for Idle Air Flow Compensation Percentage (I think that's what is called) That PID should get reset to 0. If I build the vehicle as a 2008 I'll see the PID, but it stays at the original value when resetting/relearn the idle speed.

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Geoff Diagnostician
Hawaii
Geoff
 

10-4. thanks

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Scott Owner
California
Scott Resolution
 

I appreciate the replies. It took some navigating to find it, but it is on this tool. At least on a Solus Legend you would click on - - OBD-II/EOBD Icon - OBD Diagnose - $0A Display PDTC I think the best option is an inexpensive tool to read the DTC's that picks up on the PDTC's at the same time. Thanks again!

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Michael Diagnostician
Arizona
Michael
 

Well reading the code is one thing getting rid of the permanent code requires that you have 2 concurrent passes. Which means all the factors needed for the computer to run and complete the evap test must be able to run and finish 2 times in a row. if it runs it once and thenthe car is taken down the street to the store and back it will not clear. must be run back to back and able to fully finish…

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Scott Owner
California
Scott
 

Hi Michael, I think you might have misunderstood me and what I was asking. I wasn't asking how to clear a Permanent DTC, (PDTC) I wasn't asking for help on how to troubleshoot a P0442. I was asking where to see the PDTC before bringing the vehicle for a smog test. I have factory tooling (Tech 2) which GM hasn't updated since the last Revision of 33.004. For GDS 2 they have the option to read…

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Randall Technician
Pennsylvania
Randall
 

I apologize for being a bit off topic, but this discussion seems a bit surreal to me. To our beloved residents of Monroe County Pennsylvania, the CHECK ENGINE LIGHT only matters (outside of warranty) if the owner is somehow concerned. I’ve seen permanent codes, but have never had to pursue one … and probably never will. It’s almost like I am living and working on a different planet. By the…

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Rudy Technician
Utah
Rudy
   

Scott- PDTCs are also displayed during a full vehicle scan in the Solus Legend. RTFM could have prevented this thread…. snapon​.​com/display/3871/Z…​.​pdf

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Scott Owner
California
Scott
 

Hi Rudy, Thanks! Sorry if I wasted your time here, or anybody else's time .

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Rudy Technician
Utah
Rudy
   

Scott- I have nothing but the utmost respect bud!!(Even referred a few people to your shop) Just busting your balls!!

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Scott Owner
California
Scott
 

An update to the Resolution. The EVAP line came in today and we got it installed. I would have posted the testing to verify the EVAP system is NOW sealed, but GM has gotten rid of the Snapshot Upload with Techline Connect. Going to $0A on the Snap-on shows the PDTC P0442. He's going to drive it around and once the ECM clears this he'll be ready to get the smog done. I appreciate the replies.

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Steven Technician
California
Steven
 

… has the Drive Pro ES tool that reads Generic Mode $0A, 7, 6, and 3, on the Quick Test, youtube​.​com/watch?v=aZNHgq… information.

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Rusty Owner/Technician
Massachusetts
Rusty
 

Permanent DTCs shouldn’t cause an emission test failure. At least here in MA they won’t trip a fail. I’m suspicious that the shop did a pre-scan with a tool that displays “permanent DTCs” and incorrectly advised the vehicle owner that it wouldn’t pass.

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Scott Manager
California
Scott
 

In california they fail the test.

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Tom Owner/Technician
Idaho
Tom
 

That right there was the question I wanted answered by following this thread….Thank You.

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Keith Engineer
California
Keith
   

Just a little more details (Steven discusses in his video too). The vehicle will fail a Smog Check unless: • 15 warm-up cycles have been completed since code clearing, and • 200 miles have been driven since code clearing – Sufficient operation of the vehicle would increase the ability for a DTC to reset. – Addresses situations where the vehicle has difficulty clearing the PDTC, with the…

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Steven Technician
California
Steven
 

Hello Rusty, Here in California Data mismatch and Permanent DTC's are are a valid reason for denial of a Certificate of Compliance in the I/M program.

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Steven Technician
California
Steven
 

Hello Scott, The … Drive Pro ES reads $0A Permanent DTC's. The Permanent DTC will be cleared the first time the OBD System is enabled to run the test for the offending component or system and sees the fault is no longer present.

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Tony Owner/Technician
Missouri
Tony
 

What if, after the repair, you drive the vehicle to clear the code and turn off the MIL (rather than clearing the MIL and mature codes with a scanner)… it takes two consecutive good trips to turn off the MIL on noncontinuous monitor codes. Surely a permanent code wouldn't clear in one good trip in this scenario?

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Scott Owner
California
Scott
 

Hi Tony, GM just says for repair verification - 1. Seal the EVAP system and use the flow meter on the GE-41413-A evaporative emissions system tester (EEST), calibrated to 0.51 mm (0.020 in) to determine that there is no leak in the EVAP system. 2. Clear DTCs. Conditions for Running the DTC•DTCs P010C, P010D, P012B, P012C, P012D, P0101, P0102, P0103, P0106, P0107, P0108,P0111, P0112, P0113…

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Scott Owner
California
Scott
   

Here's another chart from the BAR - look at Section E bar​.​ca​.​gov/Industry/OBD_t… I always like when things are black and white, but there are enough gray areas in this business that you could go nuts trying to memorize a bunch of things that might not always apply, because… I recently fixed a 2002 GMC that wouldn't pass smog because the EGR monitor hadn't completed…

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Tony Owner/Technician
Missouri
Tony
 

Thanks for the reference. At least GM isn't on the Permanent DTC issues list. Meanwhile I just noticed some dipshot is downvoting a bunch of comments in this thread. I wonder if that's everywhere on the site or (s)he only hates civil Permanent DTC discourse.

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Unprofessional
Steven Technician
California
Steven
 

Hello Tony, great question. Natural healing is a great strategy for clearing faults without rebuilding data for all the monitors. Mode 0A codes will in fact clear the first time the test that triggered the code passes. We already have DTC's to alert us of failures, The permanent DTC is an image of tests that have not passed the OBD, even if faults have been cleared. there is no reason to…

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Tony Owner/Technician
Missouri
Tony
 

Thanks, Steven, it's good to know that one passing test clears the permanent DTC.

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