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Vladgmru, Automotive Electrician
Category: Chevy
Satisfied Customers: 2664
Experience:  I've been working with American made cars since 1992.
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getting code c 0660 for exhaust valve circuit fault. Would

Customer Question

getting code c 0660 for exhaust valve circuit fault. Would this pertain to the solenoid itself or the control module that operates it. I just installed a new compressor/and solenoid assembly less than two months ago. vehicle is 04 Denali with 77k and autoride w aoto level. I replaced the rear oem shocks with new oem units, due to one that was leaking.
Submitted: 7 years ago.
Category: Chevy
Expert:  Vladgmru replied 7 years ago.
Thanks for choosing JustAnswer.
My name is Vladimir.
It sounds that you have a wiring issue.
There are two wires that go to the exhaust solenoid. The Orange wire is +12V power coming from the 30A RTD fuse and the Dark Blue wire is control circuit from the Suspension Control Module ( the module provides ground to the solenoid it order to operate it). I am almost sure you have a problem with the Orange wire.
Use a test light connected to ground and check for power on the Orange wire at the compressor connector.
If you do not get power, check the RTD Fuse in the underhood fuse block.
If the fuse is OK, then trace this orange wire down till you find an open circuit ( break/corroded wire).
I am almost sure you will find a promlem in the wiring harness running under the vehicle in right rear corner ( where the C450 connector is, see the picture below).
Let me know if you need more information.
Customer: replied 7 years ago.
Checked both the blue and orange wire going to the exhaust solenoid. Orange is 12 v constant, and blue is constant ground. This is incorrect right? The blue should only be showing ground when the system is letting air out? Not sure why this problem never showed up unitl the same day that i replaced the rear shocks. How could the new shocks affect the system and generate these fault codes? also there are five major harnesses on the passenger side. what would i be looking for there? where is the Suspension Control Module so that i can trace this blue wire there to see if and where its grounding out at? Thanks
Expert:  Vladgmru replied 7 years ago.
You are correct, there shouldn't be ground on the Dark Blue wire unless the control module wants so.
I do not see any relation between the rear shocks replacement and this trouble. It could be either a coincidence or something has been disturbed during this work.
You should disconnect the suspension control module that is located behind the right rear quarter trim panel and check if the dark plue wire is still shorted to ground.
You may also fing this Blue wire at the C10 terminal of the C450 connector.
See the picture I sent you in my previous reply to find the C450 connector.

Edited by Vladgmru on 2/26/2010 at 11:53 AM EST
Customer: replied 7 years ago.

traced the dk blue wire all the way to the control module. It is not grounding out anywhere. It only has a ground signal when i plug in the c2 pink connector back into the module. So the module is throwing ground down this line. I do have the service autoride light still on the dash. Do i need to reset the codes and try again? so atleast ive ruled out wiring as the issue. Ive heard in other forums i may need my module to be recalibrated/updated by the dealer. Is this possible after putting in the new shocks. I was told the shock are a revised model from the factory from the original '04 units. Wondering if a simple recalibration will fix the isse of the module leaving the exhause vale open constant. Thanks!!

Expert:  Vladgmru replied 7 years ago.
Try to erase this trouble code and see if it comes back.
Maybe you have a faulty level sensor that tells the module that the truck is sitting high?
Check the solenoid resistance, it should be 18-45 ohms.
I am not sure about recalibration, it has to be checked with a TECH 2 scan tool and Service Programming System.
Is C0660 the only code you get?
Customer: replied 7 years ago.
yes c0660 is the only code that the shop told me. I dont think it is level sensors since i never got this code before the rear shocks were installed, but i gues you never know. is it more than likely that the module has gone bad?
Expert:  Vladgmru replied 7 years ago.
I do not think the module has gone bad, at least I have never seen any problems with these suspension control modules.
Check for vent solenoid resistance to be sure it is OK.
Vladgmru and 8 other Chevy Specialists are ready to help you
Customer: replied 7 years ago.
what do you mean vent solenoid resistance, how am i testing for this? i did test the solenoid resistance at 26 ohms
Customer: replied 7 years ago.
the module is sending ground out of the blue wire at all times. the mechanic cant even reset the c0660 code, it comes right back on immediately.
Expert:  Vladgmru replied 7 years ago.
The the resistance of the exhaust solenoid valve ( 26 Ohms) is ok.
How did you find that the blue wire has ground all the time? Multimeter or a test lamp?
If you are sure that the blue wire is not short to ground on its way from the control module to the solenoid, then your control module appears to be bad.
A new module has to be recalibrated after replacing.
Customer: replied 7 years ago.
I was using my multimeter with a 12v lead and the blue wire is constant ground. As soon as I unplug the harness from the module there is no ground present on that blue wire. So I definitely think there is no possibility of it being grounded out somewhere else. weird coincidence that this is being triggered after the shock install. Literally right after.
Expert:  Vladgmru replied 7 years ago.
Hi, I do understand that you got this trouble after the shock absorbers install, but I can't find any relation. It sounds really odd.
So, do you check for resistance between the chassis ground and the blue wire with you multimeter or you check for voltage between battery + and the blue wire?
If you have a test light, could you check the blue wire with the test light clip connected to +12V battery power ( orange wire for instance)? I have to know if your test light glows when you probe the blue wire.

Edited by Vladgmru on 2/27/2010 at 9:21 AM EST
Customer: replied 7 years ago.
My multimeter shows 12 volts when across the orange wire and blue wire. just as it does across the orange wire and chassis ground
Expert:  Vladgmru replied 7 years ago.
Ok, that is right.
Just to be sure that the module provides soild ground, check the blue wire with a test light connected to power. Connect you test light across the orange and blue wires and see if it glows. Check it with the KEY OFF and with the KEY ON.
Customer: replied 7 years ago.
So you think that my meter might be getting a weak ground signal from the blue wire, enough to read a normal 12 volts, but not enough to normally operate the solenoid. Im really am hoping that the exhaust valve solenoid is the casue of the problem since i recently purchased it and will be able to have a replacement sent for no charge. Thanks. I will check with a test light in the am.
Expert:  Vladgmru replied 7 years ago.
I would like to clarify my position. I hate to replace parts by guesswork and I do not want to mislead you and cause unnecessary parts replacing.
Multimeter may mislead you testing for ground. Try the following and you will see what I am talking about:
1) Set you mutimeter for voltage testing, connect your Red multimeter lead to the positive battery terminal, hold/touch your Black multimeter lead with your left hand and touch the negative battery post with your right hand. I am almost sure you will get about battery voltage on the multimeter display.
Also, check for power on the Orange wire with the test light clip connected to ground .
The resistance you checked across the solenoid wires is OK and within the specification, so at this point I can assume it is OK.
See you later and good night!
Customer: replied 7 years ago.
i will use the test light shortly to double check for a faulty control wire circuit from the control module . I removed the compressor and exhaust valve assembly for bench testing. Compressor works fine when 12 v applied. When i apply 12v and ground to exhaut valve i hear nothing. Shouldnt i be able to hear that switch clicking the valve open and closed?
Customer: replied 7 years ago.
i will also check resistance again to make sure my readings were correct. i should get some continuity through the exhaust valve correct?
Expert:  Vladgmru replied 7 years ago.
I am not sure if it clicks loudly enough on these models, but other vent solenoids ( Fords, Lincolns) could be heard or at least felt.
Recheck the solenoid resistance( normal reading is 18-45 ohms), also check if current flows through the solenoid when you apply power and ground. If you have amperemeter, you should register about 0.4A( 400 milliampere).
Customer: replied 7 years ago.
i should still get a reading even though the lowest setting on my meter is 2000 ohms correct?, i am getting nothing right now.
Expert:  Vladgmru replied 7 years ago.
What is your meter brand and model?
How did you get 26 Ohms yesterday?
Your meter should have : 200-2K-20K-200k-20m
I think you should set your meter to AUTO( if it is possible) or to "200" in order to check this solenoid.

Edited by Vladgmru on 2/27/2010 at 8:12 PM EST
Customer: replied 7 years ago.
my meter is a cheaper protek, lowest setting is 2000. the shop said they got 26 ohms yesterday on their meter. but even on the 2000 setting it should still read atleast .00xx
Expert:  Vladgmru replied 7 years ago.
Check your test lamp resistance with your meter just to be sure that it works.
Could you tell me your Protec model #? I can't believe it has 2000 maybe last digit means Ohm and nor zero?
Sounds that your solenoid is bad and that is the main reason of C0660 trouble code.
Do not trust to what is said, check it yourself.

Edited by Vladgmru on 2/27/2010 at 8:29 PM EST
Customer: replied 7 years ago.
it is a protek d-906 and the only settings for ohms is 2000 and 2000k. yes and checking it myself has no reading. when i check resistance with the same meter on other components, i do get a reading.
Expert:  Vladgmru replied 7 years ago.
You are right, and it seems you can't check for low resistance value with this meter.
Have you checked your test light resistance with this meter? Does it show something?
Customer: replied 7 years ago.
im getting no reading from metering the test lamp. the meter stays showing 1
Expert:  Vladgmru replied 7 years ago.
Well, use another meter that can measure lower resistance and do not forget to check the Orange and Blue wires with the test light.
I am going to leave ( it is too late here, 1:40AM), will be online in 7-8 hours.
See you later.

Edited by Vladgmru on 2/27/2010 at 10:42 PM EST
Customer: replied 7 years ago.
I checked the wire with a test light, the light is very weak, with key on. Using a chassis ground the light is full brightness from the orange wire. So you are right, there is not a true ground being sent out down the blue wire from the module. I am having a replacement compressor/vent solenoid assembly sent out right now and should have it thursday. hopefully that fixes the issue. I will get back on and let you know thursday what the outcome is. Thanks!
Expert:  Vladgmru replied 7 years ago.
Hi, thanks for the reply.
Hope a new copressor assembly fixes this code. We will see.
I am looking forward to heraing from you.
Customer: replied 7 years ago.
got the compressor with vent solenoid, check ohms with my meter frist and read18 ohms. So my meter is able to read it fine, it was just a bad solenoid after all. Thanks for the help, and im definitely glad it wasnt a bad module.
Expert:  Vladgmru replied 7 years ago.
Thanks you for the reply.
I am glad it turned out as simple as a bad solenoid.
Just two more question please.
1) How long did your solenoid last?
2) Was it an original part?
Customer: replied 7 years ago.
the solenoid was two months old and was aftermarket with the compressor from Arnott Industries in FL, USA
Expert:  Vladgmru replied 7 years ago.
Thanks again and good luck.

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