check engine light

the check engine light came on on my wife's '95 Escort LX (120k miles). i just changed spark plugs. Also a while ago the airbag light was blinking which went away again (first time code 33 and last time 53) I found out what the code means - 33 Pin 7 Not Grounded at Diagnostic Monitor, 53 Internal Diagnostic Monitor Fault, but no idea how to fix it. Regarding the engine light, i assume it is the O2 sensor, since also my gas mileage dropped quite a bit, but how can i check that? I don't just want to buy stuff shooting in the dark! the idle rpm nearly stall the engine once the check engine light came on. So, does that all point towards the O2 Sensor, or could it be also something else?
One more question - the battery seems to have also a problem - i checked the voltage 12.8V (engine switched off), during start the voltage drops to about 5V, and once the engine is running i have about 14.3V
Thanks for any help

For the battery, 12.8V at rest and 14.3V with engine running are both ideal voltages. 5V during cranking is less than half of what it should be though so something is amiss. It depends on precisely where you are measuring the voltage, and during cranking that should be measured directly on the battery posts - not on the connectors, but directly on the lead posts themselves.

If it still reads 5V then either your battery has started to sulphate and develop a high internal resistance, in which case its life would now be very limited, or the other possibility would be a faulty starter motor, drawing dramatically more current than normal.

If though you get a reading of around 10.5 to 11.5V measured directly on the posts then your battery is still good, and the remainder of the voltage will be being dropped across a bad connection in the starter circuit. I'd start by removing the battery connectors, cleaning the mating surfaces with a wire brush and then smearing them with petroleum jelly or dielectric grease prior to reassembly, to inhibit further corrosion. If you're still dropping voltage then I'd remove and clean the starter end of the heavy cable running from battery positive terminal to starter solenoid B terminal - again, clean it with a wire brush and apply a protective coating. And then if you're still dropping voltage, then it would likely be at the engine end of the heavy ground strap which runs from battery negative terminal to the engine block - remove it, clean it, and apply a protective coating (the end which connects to the battery negative terminal will already have been cleaned).

I'm a diesel driver so I'll let somebody else help out on the check engine light and O2 sensor. If you don't get any answers on the airbag codes, I'll take a look at the Ford manual tomorrow and see if shines any light on the subject.

It would be best to get your CEL codes read at auto parts store, etc., to better understand your problem. Please post your code numbers for us to best be able to analyze what's going on. Just because you may have a code related to an O2 sensor doesn't necessarily mean the sensor needs replacement, but could indicate the fuel ratio isnt right, etc.

According to my Ford service manual for the '95 Escort, the two airbag codes indicate the fault conditions shown below, which differ from those which you stated above. It lists possible causes and checks for each code, but before going any further we should verify which interpretation of the code is the correct one, eh. Anybody know which one is right?

DIAGNOSTIC TROUBLE CODE 33 -- PASSENGER SIDE AIR BAG MODULE CIRCUIT HIGH RESISTANCE OR OPEN

DIAGNOSTIC TROUBLE CODE 53 -- RADIATOR PRIMARY CRASH FRONT AIR BAG SENSOR CIRCUITS RESISTANCE TO GROUND OR AIR BAG DIAGNOSTIC MONITOR FAULT

i googled these codes and didn't find a whole list for Escort but for a different model. I assumed that they are all the same for Ford models, but i guess i was wrong on that one. i am bringing the car to AAMCO today to check out the engine check light. I hope that helps me finding the problem.

I'd go to Autozone and let them load test the battery first. I think O2 sensor replacement is normal maintenance. Might be a good idea to replace it regardless.

ok - i just came back from AAMCO - they checked my codes for free. I was hoping that it is something simple like the O2 sensor, but i got this back (well, maybe it is still simple but i have no clue :smile: )
172: EGO not switching, lean exhaust B1
186: Injector pulse width high or MAF too low
Anyone knows how to fix this?!? Can the battery have something to do with it, since i am now pretty sure the battery is bad?
Any help is greatly appreciated!!

I'd replace the oxygen sensor to start with. EGO=Exhaust Gas Oxygen Sensor.

Don't forget to have your battery load tested if you have the least suspicion it's weak.