QuestionQUESTION: Trouble with my car began few weeks ago. I was driving and the engine suddenly stalled. I moved to the side lane. The car did not start right away but it start after 5 minutes. I parked the car and tried to start after 2 weeks and it did not start. It was cranking. Tried after few days and it started fine. Tried this for few days and sometimes it will start and sometimes it will not.
Today I read the codes and they are P1703, P0727 and P0722
The CEL is OFF
Thanks in advance
ANSWER: P0722 indicates a problem with the output speed sensor (pulse generator B) signal. Depending on the production date of your vehicle and the software currently loaded in the transmission control module (TCM), there may be a software update to resolve the issue. If the update doesn't apply to your car, then you'll probably need new pulse generators. This is unrelated to the condition you've described.
P0727 indicates no engine rpm signal was received from the engine control module (ECM). The TCM receives this information via a dedicated wire between the ECM and TCM.
P1703 indicates a problem with the throttle position sensor to the TCM, but according to my service information, this code doesn't apply to your vehicle.
All of the above codes store in the TCM, and you've reported none in the ECM, so my first inclination is that there's a problem with the ECM. The P0727 code supports this idea. When you turn the ignition key to the on position, does the check engine lamp illuminate? If not, it's likely that the ECM is not turning on.
It's important to not assume, however, that the problem is with the ECM itself. You could have any sort of interruption in the power supply or the ground circuit. Check the ECM fuses, the engine control relay, and the ignition switch. Also, check the power and ground wires at the ECM to verify they indeed are supplying power and ground.
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QUESTION: Thank you very much for detailed response.
Here is more information.
The car is 2002 Accent GS (2 DR), 1.6 Liter
Date of manufacture Jan 31 2002 (This was the date from the driver side door).
I could not find any fuse that said ECM but I found few fuses that say ECU (2 under the hood and 1 in from of driver seat). All of the fuses were good.
I also checked that when you put the key in ON position, all the lights turn on.
Can you please give me more information to identify the problem. I am new to this. Where is ECM located and how to check if power and ground are OK.
Where is engine control relay and the ignition switch and how to test them.
I am new to this,so any additional information will be very helpful to me. I do have a multimeter.
ANSWER: Since you report that the check engine lamp illuminates, we already know that the ECM is powering up and is grounded properly, so it won't be necessary to check those things. If you were to check those things, with the help of an electrical schematic, you'd check to see that you had 12V on the appropriate power wires when checked between that wire and the battery negative terminal (or anything metal on the car's body) and that you had 12V between a known good power source (such as the battery positive terminal) and the ground wire.
Again, if your check engine lamp illuminates, the above tests aren't necessary. I suspect that, for whatever reason, your code reader isn't communicating properly with the ECM. For now, let's check to see whether you have some of the basics necessary for the engine to run. Once we determine the nature of why the engine won't start, we can then start looking at the potential causes for that type of issue.
Check for spark. To do this, remove a spark plug wire from the plug and insert a spare plug in the end of the wire. Lay the plug on the intake manifold and crank the engine. This will best be done with an assistant cranking the engine so you can monitor the plug. Does the plug spark while the engine is cranking?
If you have spark, check for fuel pressure. (Do this only after all spark plug wires are returned to their proper place). Unbolt the fuel line from the fuel rail and remove it (guarding your eyes from any potential spray.) Turn the key to the start position and quickly return to off. Did fuel come out? If it did, this is an indication that the fuel pump is working (although not sufficient to show proper fuel pressure).
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QUESTION: The car starts most of the time and will drive. If it wants to start, it will start right away other times no matter how many time I try, it won't start.
So I was having this problem and CEL was OFF. Even though the CEL was off, I got P1703, P0727 and P0722 codes. From your first reply, these codes are not related to starting problem.
I was trying to figure out the if people had the same problem and it seems like lot of people had similar problem. Some were suggesting replace main engine relay and few sensors. I wanted an expert advice loke yours before I start replacing parts.
AnswerIf you want to find the problem, you'll need to do your testing while the symptoms are occurring; otherwise all tests will have good results. If I had to guess, I'd suspect a crank sensor. But that's just a guess. Could be the ECM relay. Could be an intermittent open circuit in the ignition coil. Could be the fuel pump. Could be a wiring issue. You get the picture. That's why I'm recommending some tests that'll give us an idea of what sort of problem is occurring. I, too, don't want you to go replacing parts that may not solve the issue.
It was my assumption that the check engine lamp illuminated with the ignition in the on position when the symptoms were occurring. If this is not the case, then we need to go back to testing power and ground at the ECM (while the condition is occurring).
