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GMTechBernard, Shop Foreman - GM World Class Tech
Category: Chevy
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Experience:  GM
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Hi, I have 2003 cadillac deville. 1) The check coolant ...

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Hi, I have 2003 cadillac deville. 1) The check coolant level always comes on. The coolant level is fine. What could it be? how do I reset? 2) check engine light on I believe it says secondary air injection. I will put on the code tester for number.   Can you give me some insight. This is my father in laws car and its driving him crazy in turn driving me crazy. HA HA

If the coolant level is correct, then the level sensor is likely suspect. The level sensor is part of the coolant jug assembly, and would require replacement of the jug, it plugs in at the bottom:



As for the secondary air injection code, first you want to check the fuses. If the air pump sucks up some water, it will blow the fuse.

Then you want to check your vacuum lines. There is a shutoff valve going to the front exhaust and one to the rear exhaust, and they are both controlled by vacuum. Sometimes the vacuum lines can fall off or crack and not allow the valves to open.

If thats all OK, check to see if you hear the pump come on. When you first start the car, especially after not being started for awhile, you should hear the pump run for a minute or two. Sounds like a small motor, it kinda whines/whistles like a hair dryer or little supercharger. If you hear it come on for a minute or two and shut off, then the air pump is obviously coming on and it may be one of the shutoff valves that failed. Its common for the diaghram inside the valve to rupture which prevents the vacuum from letting it open.

This is where the front valve is located, the rear valve looks the same and is over the center of the back valvecover:


Customer: replied 8 years ago.
Reply to GMTechBernard's Post: Thanks

Coolant issue:
1) checked all fuses. All good.
2) I checked plug harness no power even on one side. Shouldn't there be? at least coming in and if switch bad would not be coming out. where might be the issue?

Codes I ran check:

Po 340 camshaft pos sensor bank 1 malfunction

po 410 second air injection system malfuntion

po 420 catalyst efficiency below threshold bank 1

Then 410 and 420 repeat on scanner w on diff showing a pd in window.

I checked what you said. I had one question directly in back of engine is a small black hose and one larger rubber hose connected to looks like a vacumm circle. These two are very loose. The lower black hose has a hose clamp but not upper(very loose) small elbow on vacumm very loose.

Thank You for your time and I will compensate.


As for the coolant level, it sends out a very low voltage from the cluster to ground. The easiest way to diagnose is to put a jumper wire between the two terminals and if the message goes out, the level sender is bad.

The P0420 means you have a bad catalytic converter, and is covered under the Federal 8 year/ 80,000 mile warranty. If you have 80K or less, you can get it repalced at the cadillac dealer at no charge.

Customer: replied 8 years ago.
Can the coolant message come on if it is too full. I spilt some out while getting harness off and put it all back and the message seems to be gone.

I just changed caty. conv last year because it was just over 80k but now at 100k I did put an after market pump in.

How about the lines in back of engine. They are related to vacumm should they be tight?

One last question at about 50-60 he gets a shimmy on brakes changed pad rotor not too long ago. looked at this morning seem fine. could he have warped rotors. (they were advance autos)

The message won't come on if too full, only low (or bad).

Aftermarket cat converters rarely have enough Oxygen Storage Capacity to satisfy the stringent diagnostic parameters of the On-Board Computer. On many of the newer cars, only a GM converter will work. You could do a search on-line for "O2 Simulators". They "trick" the computer into thinking the converter is working and prevents the P0420 from setting.

The lines on the back of the motor need to be tight. Air of Vacuum leaks can prevent the system from working properly.

As for the brake shimmy, some aftermarket rotors are better than others. If you spend $15 per rotor, chances are, they will warp rather soon. When it comes to brake components, you really do get what you pay for. Instead of replacing them, you can have them resurfaced.

GMTechBernard and 5 other Chevy Specialists are ready to help you
Customer: replied 8 years ago.
Reply to GMTechBernard's Post: Thank you so much for your help today.

After I tightened the vacumm stuff no more lights came on nor did the o2 sensor. Although I only drove it for about 1 hr.

How do you install an 02 simulator if It comes on again. I will need a sticker at end of month and the engine light cant be on.

Im hitting accept after this message.

Thanks Again.