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sprinkles08, ASE Certified Technician
Category: Cadillac
Satisfied Customers: 22983
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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05 cts. no start. key stuck in ing. no ck engine light. no

Customer Question

05 cts. no start. key stuck in ing. no ck engine light. no shift indcator lights. If the check engine light is on an the shift indcator light is on it will start. Also getting a UO100 an U 1016 code
Submitted: 1 year ago.
Category: Cadillac
Expert:  sprinkles08 replied 1 year ago.

Hello and welcome to JustAnswer!

Your powertrain control module is down. The PCM is the module that controls all engine functions. Without the PCM it obviously isn't going to start, it isn't there to read transmission range sensor position, and if it isn't awake then the engine light won't do a bulb check at key on.

The problem could be an internal failure in the PCM itself, which is most likely, or it could be a loss of power or ground to it due to a wiring or power distribution issue. What will need to be done is test the PCM powers and grounds at the time it is down and if ok then the it can be condemned.

Customer: replied 1 year ago.
All power an grounds on trans moldule are good. Changed ecm. same results. There has to be a real way to trouble shoot this.
Expert:  sprinkles08 replied 1 year ago.

The PCM doesn't communicate with a scan tool, correct?

You load tested the PCM powers and grounds?

Customer: replied 1 year ago.
I just purchased a 05 CTS 3.6 a/t and I'm having a difficult time resolving this issue. It seems related to the common theft deterrent issue...My vehicle does not crank. When I turn the key on, the theft light comes on, then turns off. About 30 seconds later, it will illuminate again and a message "service theft system" will be displayed on the radio display. The typical coolant/fuel gauges not working and the TC lamp illuminated, and the shift indicator not illuminated.Codes in PCM/TCM were U1000/U0100I decided to throw a dart at it and replace the ECU, as most of these cases are fixed this way. I ordered a reman ECU off ebay which they programmed to my vin. Here's the strange part that I've never read or heard about: As I was attempting to perform the key learn procedure, I noticed the theft deterrent light wouldn't turn off. I waited longer than 10 mins, and the light stayed on. I continued on with the procedure regardless and repeated 3 more times, with no luck.Now for the weirdest part... With the ignition on, if I loosen the negative battery terminal and play with it, ie. move it around for a bit, I will hear the throttle body actuator energize. When that happens, everything works as it should, The gauges work, no security/TC light, the shift selector will be illuminated, and the car starts and runs perfectly fine. I will be able to start the car again if I do so within 5 minutes. If I wait any longer, it will have the same issue.I'm thinking I have a bad ground somewhere. I have a new battery (750 CCA) and replaced the negative battery cable. I cleaned off all ground points to chassis and ecu-No help. I'm going to check the ground wires at the ECU and DIM for any high resistance. Possibly replace the DIM? I just think it's strange that the theft lamp doesn't turn off after 10 mins.Anyone have any other ideas? Or ideally anyone who had these same exact symptoms and
Expert:  sprinkles08 replied 1 year ago.

The PCM doesn't communicate with a scan tool, correct?

You load tested the PCM powers and grounds at the time the problem was present?

Customer: replied 1 year ago.
What i am getting is a U0100 code on my scanner. I have checked the power an ground input to the ecm with the harness pluged in an the key on,with my volt meter. Main rely ground is good #24. #1 Ing voltage is good. # ***** ing voltage is good. # ***** Battery voltage is good. # ***** accessory voltage is good. #3 ing voltage is good. An # ***** ground is good. Also went to the Theft deterrent module an checked for power an grounds. they are all good. I have 3 things down. Wouldnt it be best to got to 1 system an start from there??
Expert:  sprinkles08 replied 1 year ago.

Does a scan tool communicate with the PCM during the no start condition?

What module is the U0100 setting in?

Customer: replied 1 year ago.
No response from ecm.
Expert:  sprinkles08 replied 1 year ago.

While it's in that state, that's when you tested the PCM powers and grounds? The only time testing can be done is when it shows PCM communication isn't possible.

If the powers and grounds are good then the next step would be to check the PCM bus voltages during the no response.

Customer: replied 1 year ago.
put the new ecm in it again today any every thing came up an worked. I think its going to be in the ecm plug.Becouse all the power an grounds were there when it was not working.
Expert:  sprinkles08 replied 1 year ago.

Yes, it's possible that you're losing a power or ground because of an issue with a connector pin or a terminal crimp.