Service Engine Soon light



I have a 2002 LeSabre with 50,000 miles, and the “service engine soon” light came on. The mechanic’s code book said it was an EGR valve. I tested it with my Actron OBD II AutoScanner and got a code of P1404. I took the car to my local mechanic. Their test also said EGR valve, so he took it off & cleaned it and the light didn’t come back on. We started driving it again, but the light came on again after about 30 miles. I took it back to him and he cleaned it again and said the valve seems to be moving freely and he didn’t want to replace it unless he was sure that’s what the problem was. I also have another Buick Lesabre, also a 3.8 motor, so I took the EGR valve from it and put it in the 2002 and the light still came on again; however, the light doesn’t come on in the other LeSabre. I don’t want to spend about $200 on this part without knowing for sure that’s the problem.


It’s probably the flow rate sensor, but you don’t have to guess at it. There are troubleshooting procedures that will narrow the problem down to the faulty component or wire.


Thanks! Can you explain what that does & the troubleshooting procedures?


Carefully cut a 1" long piece of black tape and put it over the light…

If you must pass an emissions test, clear the code and try to get it tested before it comes back on…Failing that, Carefully examine the area around the valve and determine the path of flow…Exhaust gasses are being fed back into the intake manifold. Sometimes a metal tube is used to transport these gasses. Remove it and ream it out with a coat hanger to remove any deposits that may be restricting flow. Ream out all the EGR passages you can get to. Remove the debris with a shop vac. MAYBE that will make the smog-gods happy…


You can get the instructions for checking and troubleshooting the egr system from the repair manual, and from online services like


You may find free testing info in Autozone’s online repair manuals.

It think that at this point you can be pretty darned sure that your actual valve is just fine. You’ll have tubes going to and from the valve. Those tubes and the passages to which they connect have to be clean/unblocked. Connected up to the thing somewhere is some kind of a sensor and a solenoid. These need to be checked & probably cleaned. The manuals should have the specs on voltages and resistances and such.


These folks explained it better than I could

Do not put tape over the CEL light. You’d be disabling a warning system that could prevent a simple future malfunction from becoming a destroyed engine.