Question:
HELP: 2011 Mazda 3 won't start; no crank. Immobilizer Issue?
AJ
2019-04-22 00:23:21 UTC
Hi,
My little sister has been having issues with her 2011 Mazda 3 Hatchback. Where her car would have trouble starting; no crank. This is an intermittent issue where if she waited several hours it would start up again. However, this intermittent issue became permanent in March 2019.

09/17 Sister moved to SD and issues started. Brought to a Mechanic A where they replaced the starter however the issue continued. Brought the car to Mechanic B where they stated that the car was having communication issues with the cluster. The car’s cluster was replaced, and the keys were reprogrammed.After a few weeks her car was up and running without issue.
10/18 The intermittent starting issues came back after ~ a year. Issues continued through March 2019
11/18 Check engine light came on. Went to Autozone to check the code. It gave the code: U0100 which described the issue as the ignition on or with the engineering running the PCM detected a serial communications error. Check engine light went away on its own after a few days.
12/18 Car had trouble starting; Cranked. Replaced with a new battery. Car started again.
03/19 Sister came out of class and her car did not start. Waited over 5 hours and it still did not start. She decided to have it towed to her apartment.
04/19 Search on the forums and it was noted that replacing the #20 and #21 40 Amp Fuses were reported to solve the issue. Changed the fuses but the issues continued.

Any help is appreciate! Thanks!
Three answers:
The Devil
2019-04-22 02:35:12 UTC
Infested with gremlins Lookit: https://www.obd-codes.com/u0100
2019-04-22 01:02:58 UTC
Take to Mazda dealership. They know about the problem more than any other shop. Let them fix it otherwise they should LEMONIZE YOUR CAR...OR something. It is their problem. Be RealBitchy about it. Don't let them walk over you.
STEVEN F
2019-04-22 00:59:24 UTC
Based on your description, the PCM is bad.


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