No start/OBD II Link Error
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No start/OBD II Link Error
Hi Everyone, My 2004 Jeep grand Cherokee in-line 6 died while on the freeway. Got it home plugged in the scanner and got a linking error. Started disconnecting sensors and still got a linking error. In addition to this my gas gage will not move and my check engine light takes about 30 seconds to come on. Changed my CPS still no start. I also checked for spark during cranking no spark. Anyone have some Ideas on how to get the engine started.
#2
Form a typical JGC 1999-2004 schematic:
I would first verify for certain that I had a good battery. It looks like the power for spark goes through a 15 amp fuse (#26) that feeds the shutdown relay (BATT 14A), both are inside the power distribution center, then it travels to the coil rail, from the coil rail 1capacitor for each bank (side of engine) are shown, then the feed goes to the 8 coil packs on top of sparkplugs. With the ignition key in he run position and using a 12 volt test light I would test for power to the in side and out side of fuse #26, if that was all good I would test out relay # BATT 14A.
I would first verify for certain that I had a good battery. It looks like the power for spark goes through a 15 amp fuse (#26) that feeds the shutdown relay (BATT 14A), both are inside the power distribution center, then it travels to the coil rail, from the coil rail 1capacitor for each bank (side of engine) are shown, then the feed goes to the 8 coil packs on top of sparkplugs. With the ignition key in he run position and using a 12 volt test light I would test for power to the in side and out side of fuse #26, if that was all good I would test out relay # BATT 14A.
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Tony270 thank you for the reply. I checked the fuse and it was good the battery is 12.3 v I've been turning over the engine. I checked both sides of the fuse #26 in the PDC with the ignition on and both sides are dead, no light. I also verified the test light worked, it did. Any other suggestions would be great. Any chance of posting the wiring diagram?
#4
They don't want us posting copyrighted material, I can draw a diagram.
I was off, instead of fuse 26 feeding the Automatic Shut Down Relay it is the other way around. The power for spark travels through the ASD relay, then through fuse 26 to the coil rail, then to the coil packs on the sparkplugs.
You need a multi meter to test out the relay, or you can quickly test for power to the ASD relay with the test light, with the key in the run position see if there is power that feeds BATT 14 under the ASD relay.
I was off, instead of fuse 26 feeding the Automatic Shut Down Relay it is the other way around. The power for spark travels through the ASD relay, then through fuse 26 to the coil rail, then to the coil packs on the sparkplugs.
You need a multi meter to test out the relay, or you can quickly test for power to the ASD relay with the test light, with the key in the run position see if there is power that feeds BATT 14 under the ASD relay.
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well I checked the ASD rely for power with a thst light and key on. No power in any of the slots. I was also looking at a wiring diagram and found the fuel gage is on the same cercit. I am leaning to the PCM. I checked the MAP, Throttle sensor, injectors all are receiving under 5 volts and the grounds are at 0'
#6
I will post the more of ignition circuit tomorrow. If I'm not mistaken the ASD relay is only energized when the ignition key is in the run and start position. You need to trace the circuit back to the ignition switch at the steering wheel. I don't think the other components are related to spark at the cylinders.
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if I am getting power to the sensors I mentioned, wouldn't that mean I am getting power from the ignition switch to the PCM? Could it be during the start and run circuit. I will check the ASD rely circuit, (rely removed) while some one cranks the engine. This way I can tell if the power gets to the ASD during the start cycle.
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#8
If you look at the ASD relay diagram it is a straight through circuit, it only powers one pole/contact inside the relay. The ADS relay doesn't power more than one circuit like an ISO starter relay.
The ADS relay is used to cut power to the firing system when the engine is cut off. When the key is shutoff power us interrupted to the ASD relay to prevent the possibility of fire inside the engine compartment caused by an electrical short. I am not a jeep expert, I'm familiar with function and operation of most common starting and charging systems used in domestic and foreign vehicles.
The power circuit that powers the ADS relay needs to be traced back to the ignition at the steeting wheel. A failure in the fuel pump, transmisson, etc is not going to effect the ASD relay for the ignition firing system, I think that's how your looking at it.
The ADS relay is used to cut power to the firing system when the engine is cut off. When the key is shutoff power us interrupted to the ASD relay to prevent the possibility of fire inside the engine compartment caused by an electrical short. I am not a jeep expert, I'm familiar with function and operation of most common starting and charging systems used in domestic and foreign vehicles.
The power circuit that powers the ADS relay needs to be traced back to the ignition at the steeting wheel. A failure in the fuel pump, transmisson, etc is not going to effect the ASD relay for the ignition firing system, I think that's how your looking at it.
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I went out with a test light again today and checked the ASD relay plugs and found power to the plug that corresponds to #30 on the relay. I believe this is power. Must have missed turning on the key yesterday when I checked it, ( do I feel stupid)! I also pulled all the fuses and found a 20 amp fuse blown, (#10 in the fuse box;adj pedal sys). Waiting on a car to go and get a new fuse.
#11
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The ASD relay is energized by the PCM when it gets a signal from the CPS telling it you're cranking the engine. The relay controls power to the ignition and fuel injector circuits. The PCM also controls the fuel pump relay the same way. The relay holding coil is 5 volts and the output contacts are 12 volts. The whole reason for a relay is so a 5 volt digital signal can switch a 12 volt circuit. The ignition coils and injectors are supplied with 12 volts constantly and are switched by digital drivers in the PCM grounding them or breaking ground to control them. The injectors are grounded to supply fuel and the coils are un-grounded so the magnetic field in the coil breaks down and creates the high voltage spark. A digital driver is nothing more that a solid state switch.
When the engine is running, the crank sensor give the PCM piston position and the cam sensor tells the PCM which cylinder to fire. The actual timing and mixture parameters are set by the PCM reading all the other sensors.
Now, are you totally confused?
The dash gauges are activated by the PCM. If any of the gauges are dead, the PCM isn't receiving the information. A lot of weird stuff happens if the PCM doesn't get a constant voltage supply. I'd hate to have you condemn the PCM for a loose connection somewhere. That would be like throwing your computer away because of a faulty power cord.
When the engine is running, the crank sensor give the PCM piston position and the cam sensor tells the PCM which cylinder to fire. The actual timing and mixture parameters are set by the PCM reading all the other sensors.
Now, are you totally confused?
The dash gauges are activated by the PCM. If any of the gauges are dead, the PCM isn't receiving the information. A lot of weird stuff happens if the PCM doesn't get a constant voltage supply. I'd hate to have you condemn the PCM for a loose connection somewhere. That would be like throwing your computer away because of a faulty power cord.
Last edited by dave1123; 03-12-2017 at 10:53 AM.
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Ok so I got my new PCM in and installed it, It started up! Let it run for 15 minutes as instructions stated, (wow this is great). Took it on a test drive all is good. Drove 64 miles and the Jeep started surging. I pumped the accelerator and it got me another mile and died. Tried to start it and it would start up and die in about 5 seconds. The gas gage again went to zero and the idiot light is on. The alarm idiot light is on. I am getting an error link when I scan the system with my scanner. I do believe I got a bad PCM. Fortunately I have a warranty.
#13
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Whoa! Dang! I would have to see that one in front of me. Sounds like the pcm is actually NOT the problem, although it MAY be getting taken out by the problem.
The link error does usually mean a bad pcm, OR it can mean bad harness connection. Much has been written about other models with the loose plugs, etc etc.
I would start by checking the wiring harness with a tooth comb. They sell those on Ebay (kidding). A good strong big battery powered work light that gets in there. I would do a LOT of electrical troubleshooting here and first comes to mind is a wire shorting against a hot manifold. Check that all the emissions devices have +5VDC on them with the key on.
I would also be checking compression and for a head gasket. Check for a coolant leak with a pressure tester. Pull all the plugs and take a look. Check fuel pressure with a pressure tester.
I temper these suggestions by saying I am by no means familliar with the 2004.
The link error does usually mean a bad pcm, OR it can mean bad harness connection. Much has been written about other models with the loose plugs, etc etc.
I would start by checking the wiring harness with a tooth comb. They sell those on Ebay (kidding). A good strong big battery powered work light that gets in there. I would do a LOT of electrical troubleshooting here and first comes to mind is a wire shorting against a hot manifold. Check that all the emissions devices have +5VDC on them with the key on.
I would also be checking compression and for a head gasket. Check for a coolant leak with a pressure tester. Pull all the plugs and take a look. Check fuel pressure with a pressure tester.
I temper these suggestions by saying I am by no means familliar with the 2004.
Last edited by 97grand4.0; 03-20-2017 at 05:54 AM.
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Well I am back. I put in the new PCM I received and ,(wow) I got codes. P117 and P122. Let me start by saying I checked the 5V to the TPS and got 5v check signal current and it moves while the butterfly valve is moved. I am at a loss. start the jeep and idles fine push on the accelerator and the engine sill hesitate and die. Changed the fuel filter and still dies in the same fashion. Anybody have some ideas??
#15
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Well I am back. I put in the new PCM I received and ,(wow) I got codes. P117 and P122. Let me start by saying I checked the 5V to the TPS and got 5v check signal current and it moves while the butterfly valve is moved. I am at a loss. start the jeep and idles fine push on the accelerator and the engine sill hesitate and die. Changed the fuel filter and still dies in the same fashion. Anybody have some ideas??
122 as it seems you know is the TPS. Both those items are fed by the same +5v, did you check the wiring harness by the CTS? That has been known to burn against the manifold.
Last edited by 97grand4.0; 03-28-2017 at 03:08 PM.