Joined
Apr 21, 2012 · 39 Posts
Discussion Starter · #1 ·
Sep 14, 2013 1999 Jeep Grand Cherokee Limited. 4.7 v8. 240000 miles+. Jeep started missing towing a light trailer up a grade, engine was heating but not to redline. Stopped and shut off then could not get a restart. Fuel pump runs and has pressure at the fuel rail. Cranks but sounds to be loading. Fault code indicates Cam Position Sensor P3040. I replaced the sensor and
confirmed 5v power at the connector as well as a good ground and no shorts indicated. Secondary problem not likely related is failed harness in the drivers door. Any help??? Joined
Dec 18, 2009 · 8,310 Posts
Did you measure the continuity of all the three wires from the CPS? Already removed and inspected the PCM connectors? Joined Apr 21, 2012 · 39 Posts
Discussion Starter · #3 ·
Sep 14, 2013 Is the PCM connector in the engine compartment, passenger side, next to the firewall? I cannot get it apart to check if that is the correct connection. Removed red lock tab and tried everything but breaking it. Once open, which pins correspond to the cam sensor wires, I do not have the wiring diagram. Also, is there any chance that the Crank Position Sensor
may be involved even though it is not throwing that code? Code shown consistently is P0340. Joined
Dec 18, 2009 · 8,310 Posts
The PCM has 3 connectors on it. It sits in the engine bay on the aft bulkhead close to the right fender (as seen from drivers position). 119.9 KB Views: 275 Joined
Apr 21, 2012 · 39 Posts
Discussion Starter · #5 ·
Sep 15, 2013 (Edited) What pin corresponds to the CPS return wire? Battery is fully charged and cranks starter as it should. Engine sounds to me as if it is not hitting in proper time which would seem to validate code fault. I will check PCM connections this AM. Thanks for the help!
Joined Dec 18, 2009 · 8,310 Posts
Disconnect negative battery terminal before removing any PCM connector.
Some googling showed that a bad battery or even a bad starter can cause this fault code to pop up. How is the
batt voltage? Do you have a charger to charge it completely?
Here is the wiring schematic for the 1999 WJ cam sensor. 119.7 KB Views: 327
Joined Apr 21, 2012
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39 Posts
Discussion Starter · #7 · Sep 15, 2013
Thanks, I will be back on it this afternoon.
Joined Apr 21, 2012
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39 Posts
Discussion Starter · #8 · Sep 16, 2013
Wires from the PCM check out OK. Still getting JUST the cam sensor fault. Thinking about trying another sensor just in case it was bad out of the box (stranger things have happened). What might be my next move? I really can not afford to replace the ECM without knowing that is the problem. Anyone have ANY other thoughts? I am going into my second day of
missing work now.
Joined Dec 18, 2009
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8,310 Posts
Sometimes non OEM sensors can cause problems, but wonder if it would be the case here. There should be a possibility to measure the cam sensor, just google this first.
Crank sensor would give the same problem, but since you don't have any code from that one, i would not suspect it. Does the tachometer show rotation when trying to
start? If yes, then the crank sensor should be ok.
Joined Apr 21, 2012
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39 Posts
Discussion Starter · #10 · Sep 17, 2013 (Edited)
Good tip. I will see if it is registering.
****Cranking engine does NOT indicate anything on the tach gauge. Guess I will pull the starter and install a new crank sensor this morning.
Joined Apr 21, 2012
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39 Posts
Discussion Starter · #11 · Sep 17, 2013
Tried new crank sensor. No luck. Same no start condition, still throws a cam position sensor fault. Going to try another cam sensor in the off chance that the first one was bad out of the box. Don't know where to go after that.
Joined Dec 18, 2009
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8,310 Posts
If the second cam sensor gives the same result, then there is not that much left what can be wrong. Did you use Mopar sensor?
Did you measure all 3 CPS wiring to ground as well, to be sure that its not a wire insulation problem?
Further then that, i can only come up with the PCM, or a mechanical problem inside the
engine. I have never tried it, but if its possible to see the cam sensor target wheel through the cam sensor hole (with a small mirror and flashlight), you could see if the target wheel is turning when you turn the crankshaft by hand. You can put a large socket on the vibration damper bolt and turn it clockwise. Then at least you are sure that the target wheel is not loose or any other mechanical problem prevents it from turning.
Joined Apr 21, 2012
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39 Posts
Discussion Starter · #13 · Sep 17, 2013
Yes, checked all three wires for short to ground or each other. Harness seems clean. Wondered about internal mechanical failure as well. Not having a lift, it is going to be tough to visualize the trigger through the sensor hole. Guess I will try but looks like the Jeep is dead at least until next weekend. Thanks for all your help. Please keep an eye on
this thread for a while as I am not giving up yet.
Joined Nov 22, 2009
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9,281 Posts
Just to rule one more thing out, check the G200 ground connection (inside the center console). Very common in WJ's for this to be loose/rusted. (G200 is the ground for the cluster, BCM). 56.5 KB Views: 247
Joined Dec 18, 2009
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8,310 Posts
If it will be impossible to see the cam sensor tone ring, then the only way to see it clear is by removing the valve cover.
The ground lug G200 where Milous was talking about, also supplies the ground to the SKIM, the imobilizer module, besides for many other components. How is the SKIS key symbol on the instrument panel, is it
coming on when switching ignition in run and will go out soon thereafter?
I don't say that this ground can't be the problem, but also don't see any interconnection with it to the stored CPS fault in the PCM.
Joined Apr 21, 2012
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39 Posts
Discussion Starter · #16 · Sep 19, 2013
I think we both may be missing the obvious here. If the Jeep jumped time or broke the timing chain (unlikely as it failed with a miss then no restart, not a lockdown), would it likely not show the same cam sensor position fault?
Joined Apr 21, 2012
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39 Posts
Discussion Starter · #17 · Sep 19, 2013
I should add that, yes, the security symbol indicates as it should and goes out. I checked my door frame bus wireing (earlier post) and it came back clean. At this point really thinking either computer or internal.
Joined Dec 18, 2009
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8,310 Posts
I think we both may be missing the obvious here. If the Jeep jumped time or broke the timing chain (unlikely as it failed with a miss then no restart, not a lockdown), would it likely not show the same cam sensor position fault? Not sure what you try to say here. You still have the same cam sensor
fault code. The fault code you are having is regarding the cam position sensor circuit, which seems to be electrical, but the PCM is looking for pulses from the cam sensor, because it sees the pulses from the crank position sensor. If for whatever reason the target wheel doesn´t pass the cam sensor, the PCM doesn´t know this, but probably will suspect something wrong electrically.
I would at least check the mechanical part out, before buying an other PCM
Joined Apr 21, 2012
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39 Posts
Discussion Starter · #19 · Sep 25, 2014
Allright. Gave up on this last Fall and bought another used Jeep (98 6cyl). Back into it now assuming timing chain issue. NOT an electrical issue. Engine is apart to the cams exposed. Chain was thrown completely off the right side (cam position sensor side) cam drive gear. Still in place on the left side but likely has "jumped" teeth. How do I set TDC (I
understand that I ultimately need exhaust but finding compression first is likely the way to go)??? Compression tester is showing me nothing turning by hand (only option unless I spin the engine with a drill/impact driver). I am betting everything is out of sequence. Where do I start? I have not pulled the timing chain cover yet because I wanted to see the TDC mark on the balancer.
Joined Dec 18, 2009
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8,310 Posts
The 4.7 being an interference engine, you can expect some bend valves. 640.6 KB Views: 153
The left and rights chains are independent from each other, so one side probably is still set ok. Attached the manual pages for setting the timing.