ECU Replacement Recommended by Mechanic - Is it Necessary?

Discussion in 'Renegade Stock Tech' started by Lotus Lake, Oct 5, 2021.

  1. Lotus Lake

    Lotus Lake New Member

    Jun 21, 2020
    Los Angeles
    Hi folks,

    Has anyone had ECU-related issues with their Renegade?

    My wife has a 2016 75th Anniversary Renegade (1.4L turbo, manual transmission). A couple weeks ago the Malfunction Indicator Light (check engine) on the dash lit up. I had the code checked and it said the knock sensor was malfunctioning. I had it replaced, had the code wiped, and a couple days later the light came on again. I took it in again and the code still read that the knock sensor was having an issue. The mechanic (indie, not a dealer) checked the knock sensor and the harness/wiring and it all seemed to be working, so he came to the conclusion that the ECU is bad and needs to be replaced because it's not communicating with the sensor properly. I've never dealt with ECU issues on a vehicle before, so I have no prior experience with it. Does it make sense that he'd reach this conclusion this way? Are there tests that can be done to check for sure that the ECU is bad or do you just reach that conclusion when you get codes for parts that are not broken?

    I called one of the dealers and the gentleman I spoke with said that it might need a software update, but the mechanic said updates don't usually fix an issue like that. I'm not sure who to believe in this case, as I've have negative experience with both dealers and indie mechanics in the past. We moved to Los Angeles a few years back and I have yet to find a mechanic I trust to work on the Renegade.

    Any insight is appreciated. I just want to make sure I'm doing my due diligence before going ahead with a repair that's going to set me back a good chunk of change...

  2. IDoMy0wnRacing

    IDoMy0wnRacing Well-Known Member

    Apr 18, 2019
    Pioneer, California
    It can be a corrupt file causing the DTC, and a software update could fix the issue.

    If the knock sensor is working properly, and the wire harness hasn't been compromised, to include the harness connector at the PCM, then yes, the ECU could be failing.

    The Power Control Module (PCM) is a single module which houses both, the Engine Control Unit (ECU) and the Transmission Control Module (TCM). The PCM sits in the engine compartment. It is exposed to the elements of the weather.

    I would, turn off the ignition (verify), disconnect the battery, unplug the PCM wire harnesses (both of them) and check for burnt or corroded pins. Check the harness connector(s) and the PCM for missing, burn and/or corroded wire connectors and pins.

    Sometimes, the simple act of unplugging the connectors and plugging them back together will ensure proper contact between the wire harness and the PCM, which could help correct your issue.

    If you don't find any issues with the PCM Pins or with the wire harness connectors, plug the connectors back into the PCM, and reconnect the battery.
    DO NOT RECONNECT THE BATTERY WITH THE PCM DISCONNECTED... Make sure that the ignition switch is off before reconnecting the battery.

    After everything has been reconnected, start and drive the Renegade around to see if the fault returns. If the fault returns, a trip the the dealer is warranted, for either a software update or PCM replacement.
    zuke likes this.

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