QuestionQUESTION: Hi Roland. My question. My 97' Caravan 4cyl DOHC. Engine will rotate but wont start. The Key Ignition codes i read are only 1,2,5,5. or 1255. It appears no power going to the PCM. I changed the Fuel Pump relay. Was wondering if the Auto Shutdown was activated?
ANSWER: Hi Roland,
Do you hear the fuel pump run (sound coming from the tank) for about 1 second when you turn the key to the 'run' position? If so, that indicates that the fuel pump relay is working. It cuts off because the engine isn't running, so that is normal. Ideally it should start up again when you are cranking it over, so listen for that if you can hear it above the sound of the starter motor.
The automatic shutdown relay powers the spark pack and the injectors, as well as the oxygen sensors. The easiest way to check its function would be to look for 12v on the dark green/orange wire at the coil pack or at the upstream oxygen sensor, which should be there just like the fuel pump (for about a second, and then returns when you initiate cranking).
Both relays will only stay closed if the engine is turning over as the rotation provides pulses from two sensors that the pcm has to
'see' for it to do the closing. It could be a sensor is bad*, or check fuse 12 in the box under the hood as it powers the asd relay.
The codes you have are not remarkable: the 12 means the battery supply to the pcm was disconnected in the past 50-100 key cycles, so unless you haven't disconnected the battery it is not relevant.
The 55 code means 'end of readout'.
*If a sensor were bad you would get an 11 or a 54 code.
So let me know what you learn further.
Roland
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QUESTION: The Fuel Pump is not making any sound. One of the reasons I was thinking the relay/fuse was hopefully blown. But I replaced the Fuel Pump Relay. No help. The van is at my work parking lot. I will do what you suggested. Probably I will know more this Friday I am taking the day off to work on the van. I will let you know how its going. a Big TY for the info!
ANSWER: You are welcome. Indeed, look at not only fuse #12 but also #17 and if you have an ohmmeter test them for continuity. It would be good to test/inspect all those fuses in the engine compartment. If you don't have a tester then for sure look carefully to be sure there isn't a crack in the internal wire of the fuse.
Your suggestion that the pcm might not be getting power is unlikely given that the starter will work. It requires an OK from the pcm for the starter relay to close.
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QUESTION: Hi Roland. Yes. The starter does turn. I am going to borrow an OBDII Scanner from a co-worker. This should help pinpointing the component(s) that maybe shorted or defective? Or just use the ohmmeter? The scanner should help right?
Roland.
AnswerThe scanner gives more detail about a specific problem, but I suspect the no start cause, what ever it is, if it isn't revealed by the check engine light (OBD-I system 2-digit numbers) it probably won't be revealed by the OBD-II system scanner 4-digit numbers. But have a look. It won't tell you about which fuse is blown for example but it might say something about a specific circuit not getting power, for example and then you have to figure out why that is.
So do check the 12 and 17 if both those are good then do take a few monment to view the others in the underhood box. The other possibilities for no start are for example if the timing belt broke then you wouldn't have compression, and you wouldn't have spark either because one of the sensors depends on the cam shaft being in motion. So you would do well to check for spark if the fuses are OK.
On the other hand, if the timing belt had broken, then you would have gotten a code 54 (cam sensor no signal), so we can set the aside, whew! So I still think fuse.
Roland
