I have a severe misfire in my engine. The check engine light is flashing contunuously.the codes that I have are:I cleared all the codes, I started the jeep, let it run for 45 minutes. then I turned it off for 20 minutes, started it back up and let it run for an hour. These are the new and only codes Im receiving areP0172P0175I received both codes 2 times, so it gave me 4 codes total but both codes were duplicates.It also seems that a couple coil packs might not be working when I unplug one on each side, the engine makes no change in idle speed . Please help and NOT sprinkles08 EXPERT PLEASE How to proceed?
Country: United StatesMake: ChryslerModel: jeep grand cherokeeYear: 2005Engine: v8
Hi, my name is XXXXX XXXXX very well could be bad coils, have you swap the 2 coils that you suspect being bad, with 2 others and seen if the miss moves to those cylinders? this is the easiest way to see if the coils are bad?
would bad coils cause these codes?
P0172P0175Wouldnt I just get a code for bad coils?
yes, if its not firing on these 2 cylinders, then it will set the rich codes, since the fuel is not burning in these cylinders,Tim
30 YRS EXPERIANCE, AUTO AND TRUCK,FOREIGN AND DOMESTIC, GAS AND DEISEL
switching known good coils are not working. Known bad coils are remaining bad when I put a known good coil in.
I have the firing order and coil placement order. We have 12 volts power on every coil plug. Please advise.
Hey tim, are you still working with me, or do I need to ask a new question to a new expert? I would rather work with you since you started helping me. thanks
then you most likely have bad drivers inside the ecm, have you checked them yet?
No, How do I check them.? I did check with a test light on each coil pack wire connector, and there is voltage on every connector but the voltage was steady on the test light, there was no pulsating or fluctuations on the test light bulb. PS. the PCM was replaced at the dealer 6 months ago.
ok, there are 2 wires at each coil one will have power with the key on, which you do, the other is the groun d, the computer grounds each coil to power it, take the ground lead for the test light and put it on the POSITIVE battery termonal, then disconnect each coil, and probe the ground wire, then crank the engine, if the drivers are good, the test light should flash, can you do this?
Should we disconnect all coils first so the engine will not start, and check for pulsing of the test light on ground signal? Because if we do it one by one , the engine will be running. Please advice is we only test during cranking but not starting the engine, or if we can check while the engine is running and check one by one?
disconnect all of them, so it wont start,Tim
ok, so the only other wire, that is not the hot wire, will be a pulsed ground wire correct?
Is this still open? I want to keep chatting with you but it says our chat session is closed?
I disconnected all the coil wires. I hooked the alligator clip from test light to + on battery terminal. When cracking the engine we did not have a pulsating ground on any of the wires, on any of the coils.
Still only getting P0172, P0175 and P0300 codes.
no pulsating grounds at all at any coil packs. What about pad O2 sensors, or what about resetting the ECU with a high tech scanner?
The PCM was replaced at the dealer 6 months ago.
Relist: Answer came too late.need answers faster
Relist: Answer came too late.he stopped responding
Hi will you allow me to help you with this problem?
yes please.... can you re read the thread?
Hi, you say there is no ground signal to any of the coils and the engine light flashes on and off , an 02 sensor failure will not cause a primary circuit problem and reboot will not help either, this is a problem with either the coil drivers on the computer or the crank speed sensor signal to the computer
is there anyway to check voltages or ground to or from the crank speed sensor signal to the computer? Is this a replaceable item?
also, is there anyway I can reload or reflash, reset etc the computer and hope it works?
Hi, yes if you have a voltmeter i can show you right now how to test it.
Yes, I have a volt meter and am very familiar with checking continuity, voltages etc. Please explain in detail. Thanks
sorry but i will need an engine size 4.7 or 5.7 litters engine?
this is the wiring schematic to the cam sensor you need to follow this test first before doing the crank sensor take a look at the diagnostic procedure see if you can follow procedures for testing this sensor, if you have any questions please ask.
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give me detailed points to check. What do I unplug the PCM and where is it located? Do I check for voltage or continuity with car off or on, battery connected or disconnected?
with a voltmeter check for 5 volts to the cam sensor ignition key to on ,do the same with the crank sensor see if the 5 volts is present let me know the results.
test with the sensor disconnected first then with it connected for both
after that do a continuity test to the cam sensor from the sensor to the computer see chart for connector view.
Is the resistance below 5.0 ohms?
OK, i GOT IT. CAN YOU TELL ME WHERE THE PCM AND CAMSHAFT SENSOR ARE LOCATED? THANKS
I need to know where the PCM and the CAMSHAFT sensor are located please and then I can perform the checks. Thank you. Waiting patiently, then ready to rate you and continue. Thanks
sorry for the delay let me send you a location please give me 3 minutes
The PCM (1) is attached to the right-front inner fender located in the engine compartment.To avoid possible voltage spike damage to the PCM, ignition key must be off, and negative battery cable must be disconnected before unplugging PCM connectors.
I will do these tests tomorrow or monday first thing. Thanks,. You are a big help and I will rate you excellent!
no problem and i am sorry for the delay.
I wanted to let you know we took the jeep to the dealer, and they replaced the PCM under warranty and it is still doing the same problem. We are now replacing the camshaft sensor and crankshaft sensor. I will keep you posted. We are also replacing the spark plugs. But there is no signal going to 4 of the 8 coil packs and the signals are intermittent. Its a wiring issue and Im almost tempted to replace the whole engine harness. Please advise. Thanks
After replacing the PCM for the second time, and also changing the camshaft position sensor and the crankshaft position sensor, we are still having the same problem. The signal wires coming from the PCM to the coil packs are intermittent and change. We have tried swapping coil packs, but the signal is like a ghost and moves around and there is no consistency with swapping coil packs trying to see if the problematic coilpack or signal travels. I need a pinout or schematic of the pcm and where the wires go? It might be a ground issue? Please advise.
Hi, sorry for the delay , temporarily lost my inter net do to weather, do you still need help?
YES PLEASE. HELP MAN. The dealer is pissing me off. They replaced the PCM Again and it worked better for like a day now its all intermittent again.
oak is it still loosing the coil signal?
yes very intermittent. some coils have the signal, and some do not, Ive verified all coil packs are good by switching them around, but the signals are intermittent to each coil. They move around
ok, let me pull out the wiring .
The 4.7L V-8 engine uses 8 dedicated, and individually fired coil (1) for each spark plug. Each coil is mounted directly to the top of each spark plug.Battery voltage is supplied to the 8 individual ignition coils from the ASD relay. The Power train Control Module (PCM) opens and closes each ignition coil ground circuit at a determined time for ignition coil operation.Base ignition timing is not adjustable. By controlling the coil ground circuit, the PCM is able to set the base timing and adjust the ignition timing advance. This is done to meet changing engine operating conditions.The ignition coil is not oil filled. The windings are embedded in an epoxy compound. This provides heat and vibration resistance that allows the ignition coil to be mounted on the engine.Because of coil design, spark plug cables (secondary cables) are not used with the 4.7L V-8 engine.
OK, I SEND YOU THAT BEFORE JUST TO GIVE YOU AN IDEA OF THE COILS OPERATION AND RELATED POWER, you have 8 coils connected in series parallel circuit this means if one coil goes bad 3 or 4 coils will be affected and this will happen to different cylinders just like you described this will also burn up the computer is the coil is badly shorted to ground.
what i need you to do is to do a resistance test on all the coils one by one document them and see if one is out of range here is the proper resistance:
Just read the resistance into each coil pack? There are 3 pins I believe on each connector? Which 2 pins do I read through?
ok there are 3 wires on each coil one is 12 volts the other is signal to the computer and the other one is signal from the computer the 12 volts wire is the primary circuit and the signal from the computer to the coil is the secondary signal ignore the other wire.
i will get back to you tomorrow around 11 am .