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Pete, Saturn Mechanic
Category: Saturn
Satisfied Customers: 27813
Experience:  17 years Saturn Technician experience.
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2002 saturn L300, 150k, goes into limp mode around 10-15mph,

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2002 saturn L300, 150k, goes into limp mode around 10-15mph, has codes p1780 and u2105, when you look at pids when failure happens, it loses communication.
JA: Just to clarify, what's the exact code? And have you tried to reset it?
Customer: P1780, and u2105, yes cleared and comes back
JA: Are you fixing your L300 yourself? What have you tried so far?
Customer: I am not so far, the crank sensor was replaced for oil concern no help
JA: Anything else you want the mechanic to know before I connect you?
Customer: no

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

Has anything after market been installed on your model here at all before this issue started?

Let me know so we can continue,thanks Pete.

Customer: replied 6 months ago.
Customer: replied 6 months ago.
No, Hello anyone there?

Have you checked battery connections at the battery as well as leading from the battery and fuse panels for any issues at all with being loose,corroded or damaged?

Customer: replied 6 months ago.

O.k.,there is a diagnostic procedure for the U code set here.This code needs diagnosed first here to locate the fault.This issue is usually either a fault with loss of power or ground to the engine computer or the engine computer itself at fault needing replaced.Below is the chart to follow to test and locate the fault here.The first step is checking battery connections at and from the battery and fuse panels for any issues as well as the grounds from the battery.

The controller area network (CAN) is a high speed system for sharping data. The circuit consists of a 2 wire twisted pair connecting the engine control module (ECM) to the transmission control module (TCM), and a second twisted pair connecting the body control module (BCM) to the ECM.

The CAN circuits are monitored continuously by the modules on the circuit. The only requirement is that the modules are in an On power mode.

Each module on the CAN serial data circuit learns the identify of the other modules on the circuit. If a module stops communicating after all module have initiated for the ignition cycle, other modules set a DTC specific for the module not communicating:
◊DTC U2105, cannot communicate with the ECM
◊DTC U2106, cannot communicate with the TCM
◊DTC U2107, cannot communicate with the BCM

CONTROL MODULE ...................................................... ID NUMBER
Engine Control Module (ECM) ............................................... 05
Transaxle Control Module (TCM) ............................................ 06
Body Control Module (BCM) ................................................. 07

Most of the time if you have no issues with powers or grounds the ECM needs replaced and programmed.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

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