XK8 SCP Bus Question
#1
09-13-2017, 08:14 PM
XK8 SCP Bus Question
I have 2003 XK8 That won't crank or run.
Checked all fuses and relays etc.
towed it to the dealer ,they suggested it might be a bad key chip. They made a new key , not the problem.
Dealer said they think it had a SCP Bus problem .
They charged me 500 for the key and scan. They then said they would have to take the dash apart to check out the wires at a cost of 1600 ,but they couldn't promise me anything for sure. I towed it back to my shop and am trying to troubleshoot the SCP Bus.
I found some trouble shooting charts that say you should have 90 and 150 ohms between pin 2 and pin 5 of the Diagnostic connector under the dash. I put a digital meter on it and it just goes from 0 to 450 ohms and never settles down. Then the next test is test the voltage on the bus pin 2 and pin 16 . The test say 3 volt mag , I get battery voltage?. I disconnect every module on the bus and get 0 volts. I plug each module in one at a time and 12 volts form any one except the instrument cluster module which is 0 volts.
Anybody happen to know what might be going on?
I don't have a lab scope but I scanned all the modules with a borrowed scanner and got 7 Body codes ( B1595,U1041,U2012,etc) 3 Locking module codes (U1135, U1041,B24D) plus codes from the Driver door module, passenger door module, etc
Checked all fuses and relays etc.
towed it to the dealer ,they suggested it might be a bad key chip. They made a new key , not the problem.
Dealer said they think it had a SCP Bus problem .
They charged me 500 for the key and scan. They then said they would have to take the dash apart to check out the wires at a cost of 1600 ,but they couldn't promise me anything for sure. I towed it back to my shop and am trying to troubleshoot the SCP Bus.
I found some trouble shooting charts that say you should have 90 and 150 ohms between pin 2 and pin 5 of the Diagnostic connector under the dash. I put a digital meter on it and it just goes from 0 to 450 ohms and never settles down. Then the next test is test the voltage on the bus pin 2 and pin 16 . The test say 3 volt mag , I get battery voltage?. I disconnect every module on the bus and get 0 volts. I plug each module in one at a time and 12 volts form any one except the instrument cluster module which is 0 volts.
Anybody happen to know what might be going on?
I don't have a lab scope but I scanned all the modules with a borrowed scanner and got 7 Body codes ( B1595,U1041,U2012,etc) 3 Locking module codes (U1135, U1041,B24D) plus codes from the Driver door module, passenger door module, etc
#2
09-13-2017, 09:13 PM
Veteran Member
If it were me I would be looking first at the grounding and power supply to all the fuse boxes on the car.
Link to Grounding test JagRepair.com - Jaguar Repair Information Resource
Link to XK8 2003 http://www.jagrepair.com/images/Auto.../jagxk2003.pdf
Link to Grounding test JagRepair.com - Jaguar Repair Information Resource
Link to XK8 2003 http://www.jagrepair.com/images/Auto.../jagxk2003.pdf
#3
09-14-2017, 07:43 AM
Veteran Member
You can start here: X103_U_DTC.pdf
2 thoughts: the instrument cluster is some form of a nerve center for all the separate buses in the car. As you have messages pertaining to CAN and SCP, the cluster becomes suspect. Any work in the area recently? These are known to fail on the earlier cars, not so much on the '03 and up, I believe...
Folks have reported corroded/burned security modules before, and an inability to start the car. It's in the trunk, I believe. Probably needs to be taken out and inspected closely. I assume if there is major damage, it is possible the bus it is on can fail. Someone on this forum posted pictures of a badly burned circuit board on one of these before, so this happens.
Might be worth posting a bit more detail of the history of the car. If none of this works, you might have to borrow the scanner again, and make a clean list of ALL codes, then look them up on Gus' site.
Best of luck, keep us posted.
PS: It goes without saying that a modern car with electronics needs a GOOD battery to run...
2 thoughts: the instrument cluster is some form of a nerve center for all the separate buses in the car. As you have messages pertaining to CAN and SCP, the cluster becomes suspect. Any work in the area recently? These are known to fail on the earlier cars, not so much on the '03 and up, I believe...
Folks have reported corroded/burned security modules before, and an inability to start the car. It's in the trunk, I believe. Probably needs to be taken out and inspected closely. I assume if there is major damage, it is possible the bus it is on can fail. Someone on this forum posted pictures of a badly burned circuit board on one of these before, so this happens.
Might be worth posting a bit more detail of the history of the car. If none of this works, you might have to borrow the scanner again, and make a clean list of ALL codes, then look them up on Gus' site.
Best of luck, keep us posted.
PS: It goes without saying that a modern car with electronics needs a GOOD battery to run...
#4
09-14-2017, 07:57 AM
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towed it to the dealer ,they suggested it might be a bad key chip. They made a new key , not the problem.
Dealer said they think it had a SCP Bus problem .
They charged me 500 for the key and scan. They then said they would have to take the dash apart to check out the wires at a cost of 1600 ,but they couldn't promise me anything for sure.
Dealer said they think it had a SCP Bus problem .
They charged me 500 for the key and scan. They then said they would have to take the dash apart to check out the wires at a cost of 1600 ,but they couldn't promise me anything for sure.
mabbas, please keep away from the dealer. Follow the excellent advice above for starters and don't throw any more parts at it until a clearer picture emerges.
#5
09-20-2017, 08:49 PM
Senior Member
Having brought a '97 with under dashboard problems back to life, I have a few "easy" ideas to get your car running. I'm not familiar with the codes you saw. So, I will ask,
1) Did you read those codes with an ELM 327 scanner or equivalent? If not, get one and a list to translate the codes. That could point you in the right direction. Also, many of the participants here are much more versed in codes than I and will be happy to help.
2) If you are confident the codes you have already read on your scanner are correct, but are not leading you anywhere, here is a reasonably simple approach.
a. Check 250A fuses in the box in the trunk. One connects to the starter motor. Since you have some voltage, I'm going to assume both fuses aren't blown.
b. Check the big braided ground cable that connects to the transmission mount under the car (or in that neighborhood...I haven't been underneath lately) to see if it is still connected.
c. The dealer seemed to think there was a problem in the key area/under dash.
Disconnect the airbag fuse when working under the dash.
It's possible the one of the grounds that come off the ignition switch has disconnected. Get a schematic (should be one on Gus's site) and find the color of the wires that go from the starter switch to ground. On the 1997 there are three - accessory, starter and always on with the key. Don't know about 2003. Maybe one has disconnected somehow.
Or maybe some other important wire is hanging visibly free.
Finally, I have discovered that because of the mysteries of multiplexing electrical items, widgets (and the car through the ignition switch) are typically switched on through the ground side as opposed to electrical widgets being always grounded and switched on through the battery B+ side. So, you can tap into wires (guided by the schematic...please don't do this randomly), prod around with a circuit testing light and occasional something will wake up if it is otherwise shorted/disconnected. I know that is repair by dead reckoning, but sometimes troubleshooting is too complicated for its own good and a simple approach can save the day.
Hope this helps. Let us know.
1) Did you read those codes with an ELM 327 scanner or equivalent? If not, get one and a list to translate the codes. That could point you in the right direction. Also, many of the participants here are much more versed in codes than I and will be happy to help.
2) If you are confident the codes you have already read on your scanner are correct, but are not leading you anywhere, here is a reasonably simple approach.
a. Check 250A fuses in the box in the trunk. One connects to the starter motor. Since you have some voltage, I'm going to assume both fuses aren't blown.
b. Check the big braided ground cable that connects to the transmission mount under the car (or in that neighborhood...I haven't been underneath lately) to see if it is still connected.
c. The dealer seemed to think there was a problem in the key area/under dash.
Disconnect the airbag fuse when working under the dash.
It's possible the one of the grounds that come off the ignition switch has disconnected. Get a schematic (should be one on Gus's site) and find the color of the wires that go from the starter switch to ground. On the 1997 there are three - accessory, starter and always on with the key. Don't know about 2003. Maybe one has disconnected somehow.
Or maybe some other important wire is hanging visibly free.
Finally, I have discovered that because of the mysteries of multiplexing electrical items, widgets (and the car through the ignition switch) are typically switched on through the ground side as opposed to electrical widgets being always grounded and switched on through the battery B+ side. So, you can tap into wires (guided by the schematic...please don't do this randomly), prod around with a circuit testing light and occasional something will wake up if it is otherwise shorted/disconnected. I know that is repair by dead reckoning, but sometimes troubleshooting is too complicated for its own good and a simple approach can save the day.
Hope this helps. Let us know.