Trouble with error code U0121
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Trouble with error code U0121
I've been battling this error code for almost a year now which is about when I bought this truck. The biggest problem is that the error code isn't on all of the time. When it does come on it will blink on and off and very rarely stays on but in one instance I couldn't start my truck after I turned it off. If I let the truck sit for a while, like overnight the truck would start. The only common trend with the error code that I can gather is when the weather is pretty hot, 85 or so with the A.C on, the code seems to be more likely to blink on off. Or when I am using my clutch a lot like in heavy traffic the error will also blink on and off. Right now its winter time and havent had the error come up for quite a while. I do know this error code is because i have a H&S chip and have had numerous mechanics look into it. the only thing they can think of is there's a short somewhere in the wiring. I am at a total loss on what to do next besides going through the wiring pertaining to the ABS. Any advice would be great.
Cargo Master
Joined: Feb 2011
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From: Forest lake minnesota
I've been battling this error code for almost a year now which is about when I bought this truck. The biggest problem is that the error code isn't on all of the time. When it does come on it will blink on and off and very rarely stays on but in one instance I couldn't start my truck after I turned it off. If I let the truck sit for a while, like overnight the truck would start. The only common trend with the error code that I can gather is when the weather is pretty hot, 85 or so with the A.C on, the code seems to be more likely to blink on off. Or when I am using my clutch a lot like in heavy traffic the error will also blink on and off. Right now its winter time and havent had the error come up for quite a while. I do know this error code is because i have a H&S chip and have had numerous mechanics look into it. the only thing they can think of is there's a short somewhere in the wiring. I am at a total loss on what to do next besides going through the wiring pertaining to the ABS. Any advice would be great.
Cargo Master
Joined: Feb 2011
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From: Forest lake minnesota
It sounds like a communication issue between the ABS module and the PCM I wonder if a reflash of the trucks computer would help. Have any of the mechanics been at a ford dealer. Also can you remove that chip and start over with a reflash?
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U0121:
U0101 X X X Lost Communication with TCM This error occurs is the CAN data communication
is interrupted between the PCM and the TCM.
Start by pulling the connections at the PCM and checking for dirt or bent or pushed in pins.
U0101 X X X Lost Communication with TCM This error occurs is the CAN data communication
is interrupted between the PCM and the TCM.
Start by pulling the connections at the PCM and checking for dirt or bent or pushed in pins.
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Reason I ask is that the cord on the dashdaqs have been known to go bad. This caused this situation on my brother's 08. Same code and random no starts. Dashdaq wouldn't power up. I could turn key on and put direct power to the starter and get the truck to start. I cleared the code with my Dashdaq and he got a new cord, flashed the tune back into the PCM with his good cord and all was well. I believe the issue was the bad cord didn't allow the tune to load correctly causing the code and random no starts and other issues.
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in response to bigpipes, the mechanics i've been to so far are just diesel specialists and no dealers but i did talk to a dealer today and doesnt seem to think that a reflash would make any differance because i was having this issue before i put the chip in. and my chip was a h&s mini maxx. he did however say that they have replaced the abs module before because they go bad. and now that i think about the pickup not starting sometimes that was in fact an issue with the chip and that has been fixed under warranty. in response to unplugging the CAN and all that I guess i would just need a little more info on what and where that is. i really appreciate all the input.
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