Last post on May 10, 2013 at 12:21 PM
You are in the Maintenance & Repair
What is this discussion about?
Fuel System, Electrical, Engine
#1631 of 1688 Re: Cnlight is looking for commission agents [obyone]
by Mr_Shiftright HOST
Mar 14, 2009 (10:28 am)
spam now in the can.
#1632 of 1688 check engine light concern
Apr 08, 2009 (11:51 pm)
My check engine light was on, code checked & cleared by a local mechanic. The code indicated PCM problem. The light came back on so I took it to a dealer to have PCM replaced (under warranty). The dealer checked & confirmed the PCM code and agreed to replace it at no cost. However, while at the shop, another code appeared that was not there before. This code indicated knock sensor and the dealer said this would cost $340. My question is, why did this code suddenly appear at the dealer? Is there a way to program this code to show up falsely? I think they may have done this on purpose and there was actually no problem with the knock sensor until they did something to make it show up. Is this possible? Thank you for any advice. Trying not to get the run around by an unscrupulous dealer.
#1633 of 1688 Re: check engine light concern [jeffreyb4]
Apr 09, 2009 (4:22 am)
Nope, you worry too much.
The engine computer is monitoring all of the sensors in the car, and using them to adjust other things and keep the engine running at optimal condition.
Some sensors are always sending back a signal, and if you don't get a signal, you know something is most likely bad. For instance, each wheel has sensor, and when the vehicle is moving forward straight the computer would see 4 signals, all at the same pulse rate. If you only got 3, then it's relatively easy to figure out that either one wheel is locked up and skidding, or the sensor is bad.
Some sensors, the computer has to deduce there are problems, by the process of elimination. Or, it can never know exactly and call out multiple possibilities. The knock sensor is a sensor where you don't normally get a signal, except when engine is heavily overloaded and starts to ping/detonate early. If the computer never receives a signal, the computer thinks that the engine is running okay....yet the engine could be severly overloaded and spark timings and mixture should be adjusted.
The analogy I'd give you is a fire alarm. You don't normally hear a fire alarm in your building, and because of that you think it's a safe working environment. However, if you walk out of the office, and it feels warmer than usual, you may think the air conditioner is not working correctly. A little bit later, if you also see and smell smoke, then you now suspect there is a fire, and then realize that the fire/smoke sensor must be defective because it never triggered and reported a problem.
So sometimes it is relatively quick and straight forward to figure out EXACTLY what is wrong. Most of the time, the engine can very quickly deduce there's only a couple of potential causes to the problem. Other times it takes more analysis or longer time to monitor multiple situations before it's able to figure out the cause. Sometimes the computer will never figure out the right cause, and it takes a humanoid to figure it out, by process of elimination or deduction.
#1634 of 1688 Re: check engine light concern [jeffreyb4]
Apr 09, 2009 (3:42 pm)
If the knock sensor is, like the PCM, germain to the Emission System shouldn't that be covered under warranty as well?
#1635 of 1688 starting problem
Jun 01, 2009 (1:27 pm)
when i turn the key nothing happens i get the dummy lights the battery is good i can jump the starter with a screwdriver and the car turns over but still wont start any sugestions on what might be the problem
#1637 of 1688 Re: starting problem [tjacks1]
Jun 01, 2009 (2:04 pm)
Ignition key switch, ignition switch relay, try a different key in case security chip in key isn't communicating with security module, etc.
Thats where I'd be starting to look.
#1638 of 1688 engine won't start
Sep 05, 2009 (6:36 pm)
The battery on my 1998 Grand Prix died and after replacing it the car will not run.
I can put a jumper to the fuel pump and it starts and runs fine. I have electricity going through the fuel relay. Is there someithing I need to reset? Is there some sensors between the fuel relay and the fuel pump?
#1639 of 1688 Re: engine won't start [dnungesser]
Sep 05, 2009 (7:32 pm)
Stepping way out of my league here, because I don't have any electrical schematics for your vehicle. You're either going to find someone who works on those vehicles and has seen that problem before and knows off the top of their head exactly what to do.....or you'll have to invest in a set of electrical schematics to diagnose it directly.
There's a couple thoughts come to mind though. I have seen in a number of vehicles where the fuel pump is controlled (turned on or off) by the engine computer. Since you replaced your battery, I'm wondering if somehow you lost the brains to the computer and you need the dealership to reload/reprogram it. The thing that leaves me a little suspicious that his couldn't be the case however, is your statement that the vehicle will run if you provide power to the fuel pump. I guess if it runs poorly this still might be the problem, but if it runs fine then it probably is not the problem.
The second thing that comes to mind is that many vehicles have a relay which turns the fuel pump off if the car has been in an accident or rolls over, to prevent a fuel leak from a broken gas line with the electric fuel pump just pumping away. I know all of my vehicles have this feature in one way or the other (some by circuitry in the engine computer, others with a standalone function board), but they are newer than a 98 so I don't know when mfg's started putting this in vehicles. Owners manuals usually will have a writeup which explains how to reset this, if the relay is triggered. Perhaps if your vehicle has this function as well, that somehow the battery reset triggered this to occur.
The last thing that comes to mind is to check ALL of the other fuses with an ohmmeter, to make sure there isn't some other fuse that blew while the battery was being jumped or replaced.
Sorry I can't help you with any specific Grand Prix info.
#1640 of 1688 Chek Engine light and smell
Sep 21, 2009 (1:03 pm)
My 2005 Honda accord has done 56k miles, for some time the check engine light has been constantly and the Maintenance required signal flashes and goes off each time I start the car. Also, I persive a smell like gas any time I accelerates fast on the highway. please what are my likely problems and how do I solve it?