You have to be careful to not cause more problems than you solve. The first problem has to do with the diagnostic fault codes. By the way, Chrysler made reading them yourself much easier than any other manufacturer. Cycle the ignition switch from "off" to "run" three times within five seconds, without cranking the engine, leave it in "run", then watch the code numbers appear in the odometer display. You can go here:
https://www.2carpros.com/trouble_codes/obd2
to see the definitions, or I can interpret them for you. The next thing is to be aware no fault code in any system on any brand of vehicle ever says to replace a part or that one is bad. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. Before we waste money on a part that is referenced in a fault code, we have to rule out wiring and connector terminal problems, and mechanical problems related to that part. Way too often we read that someone replaced the part mentioned in the fault code, and the Check Engine light turns right back on and the same code has been set.
Also be aware there are dozens of fault codes related to the oxygen sensors, and they mean very different things. Well over half of them are defects that need a properly-working sensor to be detected, so changing the sensor doesn't change the defective condition it detected.
The problems you created were caused by disconnecting the battery. Once you solve a problem that caused a fault code to set, that code will self-erase after typically 50 engine starts. The best way to erase them is with a scanner. Disconnecting the battery will not erase all fault codes in all computers, but it can erase any learned data. Most engine-related data, such as sensor characteristics and fuel trim data will start to be relearned without you even noticing, except for "minimum throttle". Until that is relearned, the engine may not start or stay running unless you hold the accelerator pedal down 1/4", you won't get the nice "idle flare-up" to 1500 rpm at start-up, and it will tend to stall at stop signs. To meet the conditions for minimum throttle to be relearned, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.
When the Check Engine light turns on, always read and record the fault codes before doing anything that will erase them, otherwise that valuable information will be lost. What can add to the frustration is when someone ignores that light for a long time. That allows plenty of time for a second, or even a third totally different problem to develop. Some of those problems are relatively minor, but can turn expensive if unwittingly ignored. There is always a long list of conditions that must be met for a fault code to be set, and one of those conditions is that certain other codes can't already be set. When the computer detects a problem with a sensor's circuit, for example, it knows it can't rely on those readings being accurate, so it suspends any other tests it runs that use that defective circuit for reference. If a second problem develops in the circuit, since the self-tests are suspended, it won't be detected, at that time. It's when the first problem, which is often the only one known to the mechanic, is repaired, the other tests will resume, and that is when the second problem is finally detected, the appropriate fault code is set, and the Check Engine light turns right back on. This is a real common source of frustration for owners of GM vehicles and their mechanics, with multiple problems in the anti-lock brake systems, but it can be just as frustrating on any car brand.
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Tuesday, October 29th, 2019 AT 5:48 PM
