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Discussion Starter · #1 ·
Hi all,

It's been a while since I have posted anything here. The past year has been fine, but then earlier this year (couple months back), I got a CEL for the very first time @41K miles. The code was P0299: Turbocharger Underboost. I took it to the dealership and they found the turbo charger had cracked and so got it replaced under power train warranty.

However now this past week, I got a new CEL showing up. The code shows up as P0420: Catalytic System Efficiency Below Threshold. :-( My engine idles rough sometimes when I coming to a stop and I can see the RPM climbing close to 1500 when I am in neutral and feet off the gas pedal.

I have made an apointment for next week with the dealership (their earliest available slot). Yesterday afternoon though while driving (heavy rains), I get two new messages show up. First about "Service Traction Control System" and then "Service StabiliTrac" or something to that effect. Then the "Traction Control" light stayed on for the entire drive home. These messages briefly came on this morning as well and then went away.

I'm getting really worried as it is raining here these days and I drive with two little children in the car.

Any ideas guys on what might be going wrong. I take good care of the car and have no mods. It is a 2013 ECO 6 spd MT. I'm at 42K+ and out of bumper to bumper warranty. None of my previous cars have every had a CEL come on. So this is new to me.

Thanks for any ideas.
 

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My ignition relay was causing these kind of erratic problems, located in that underhood Fuse/relay box. under that cover lid shows the location.

Just dirty relay contacts, with my oscilloscope was getting a jagged waveform instead of a clean sharp voltage, these computer circuits need for a proper reset and it occurred about the same mileage as yours.

Can try rebooting your Cruze, switch off the ignition, pull the key, open the driver's door and try again, maybe even a couple of times.

Here is a photo of this relay:

View attachment 203993

Just a bit of arcing on that normally open contact, burnished it and was good to go, but replaced it with a Panasonic.



Automotive stuff, those tiny contacts are rated at 45 amperes.
For 120VAC, that same contact rating would be in a five pound relay for a 45 ampere contact rating.
 

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Discussion Starter · #3 ·
Hi Nick,

Thanks for your prompt reply. That is interesting. I'll go take a look at my ignition relay and see how things go. For whatever reason, I'm unable to open the attachment you uploaded. It comes back as an error. Would you please be able to upload that photo again?

Thanks
 

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View attachment 204057 View attachment 204065 View attachment 204073

This was another little problem, crimping bare copper wire that corroded within the confines of the battery and ground terminal. Propane torch and lead tin solder took care of these problems. Was actually getting a 2.1 volt drop across that cable where it should be a maximum of 0.1 volts with a lot of the accessories switch on.

Last photo shows that Panasonic relay.

Oh, that is actually a grade 8 bolt for the battery terminal, original was an M6mm-1 that would strip out with about 3 ft-lbs of torque on it, made out of some kind of pot metal. New bolt is a 1/4"-20 so tapped that nut the same size to make it look more original, same with the positive.

Its little stuff like this that can cause you grief, if the solder dipped those cable ends, would have lasted forever.
 

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Discussion Starter · #6 ·
Thanks Nick!

I'll check out the relay. In the past I have looked at my battery cables and the ends look very well crimped. I had also scrapped up the terminals and posts and applied electric (bulb) grease on them.

Looking through my manual I see there are two ignition relays (7 & 15). Do you know which one?
Text Font Line Number Parallel
 

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Looking doesn't work, voltage drops across cables or wires do, can switch the ignition on and put the blower motor on full speed for a 20 ampere pull.

Ever see pretinned wire? Guess it depends when you were planted here, each strand of the wire is plated for corrosion protection. Haven't seen this new crap for years, all bare copper now. Ever hear of a copper oxide rectifier? Practically infinite resistance in the reverse polarity direction. We are now getting these for free with bare copper wire, it also oxides turning deep brown color, and this is exactly what I found on the inside of my battery terminals with a high voltage drop to verify it.

The end of the battery terminal is round where the wire goes in and crimped with a punch press and also exposed to battery acid fumes, yep, even a so-called maintenance free battery does this. Was covered under warranty for the negative battery cable only, the negative battery terminal is 50 mils narrower in diameter than the positive. Somebody was putting positive terminals on the negative battery and only took GM three years to catch this. Couldn't even tighten that cable terminal properly.

Look at the underside of your fuse/box lid for a far more accurate drawing than in your owners manual, apparently the guy that made that owners manual drawing needs new glasses.
 

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Discussion Starter · #8 ·
Hi all,

Just a quick update. I took my car in to the dealership Tuesday and got it back yesterday. They diagnosed it and found the cause was due to a diaphragm in the camshaft cover that was stuck open. So basically the valve cover was leaking and caused the fuel system to run lean etc.

This apparently caused all the error codes I was seeing as well as the drop in mileage and constant surging while idling. Sometimes the engine would race up to 2K RPM while coming to a stop and the clutch fully engaged or even if the gear was in neutral.

Anyway they claimed the battery negative terminal is fine. The dealership got all of this replaced under warranty and fixed. The car runs really smooth again and idle is back to around 800 RPM.

I love my dealership (Henna Chevrolet in Austin, TX) as they have so far been taking very good care of me and each time provide me with a great loner car.
 
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