Darcy1 Posted September 14, 2015 Share Posted September 14, 2015 Hello everyone I'm new to this forum and have a problem with a 2013 GU813. The truck is in derate mode. DEF gauge reads empty, tank is full. Engine light is on. Code NOX malfunction data valid but higher than normal. I suspect the DEF level sending unit. Any tests to perform to validate my prognosis?Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/41797-def-gauge-reads-empty-nox-malfunction-derate-mode/ Share on other sites More sharing options...
Darcy1 Posted September 15, 2015 Author Share Posted September 15, 2015 Replaced the DEF tank sending unit and still no guage still in derate mode. Quote Link to comment https://www.bigmacktrucks.com/topic/41797-def-gauge-reads-empty-nox-malfunction-derate-mode/#findComment-303923 Share on other sites More sharing options...
Challenger Posted September 15, 2015 Share Posted September 15, 2015 Has anyone worked on the batteries? The ACM (aftertreatment control module) power wire goes straight to the batteries. Its just a small wire terminal. Ive seen 3 trucks that had the batteries replaced and the terminal was left off. As a result the truck was in derate and the DEF tank read empty. This is the only idea I have. Quote Link to comment https://www.bigmacktrucks.com/topic/41797-def-gauge-reads-empty-nox-malfunction-derate-mode/#findComment-303932 Share on other sites More sharing options...
Mackpro Posted September 15, 2015 Share Posted September 15, 2015 Unplug DEF pump harness and check for DEF inside the harness connector. Also unplug the Turbo actuator connections and recheck. I had a turbo actuator short out the J1939 line and cause the DEF level sensor not to read as it is on the J1939 line too. Quote Link to comment https://www.bigmacktrucks.com/topic/41797-def-gauge-reads-empty-nox-malfunction-derate-mode/#findComment-303938 Share on other sites More sharing options...
Darcy1 Posted September 15, 2015 Author Share Posted September 15, 2015 Thanks for the tips people. Problem resolved. I found a broken power wire in the ACM harness about 2ft in front of the battery box on the inside of the frame rail. I'm surprised the fuse didn't blow as it was the positive rubbed through on a cross member. Repaired wire no longer in derate. I still had to clear the engine light with VCADS PRO.Thanks again everyone. Quote Link to comment https://www.bigmacktrucks.com/topic/41797-def-gauge-reads-empty-nox-malfunction-derate-mode/#findComment-303951 Share on other sites More sharing options...
dickbuick Posted November 2, 2016 Share Posted November 2, 2016 I have a 2012 GU same problem but its not the power supply went over that. Went over the J1939 link not seeing it? Any help Quote Link to comment https://www.bigmacktrucks.com/topic/41797-def-gauge-reads-empty-nox-malfunction-derate-mode/#findComment-350715 Share on other sites More sharing options...
Mackpro Posted November 3, 2016 Share Posted November 3, 2016 Heres some Mack tips on the J1939. Data Link2.pdf Data Links1.pdf Quote Link to comment https://www.bigmacktrucks.com/topic/41797-def-gauge-reads-empty-nox-malfunction-derate-mode/#findComment-350805 Share on other sites More sharing options...
Mackpro Posted November 3, 2016 Share Posted November 3, 2016 And what is the actual fault code that you are getting? Quote Link to comment https://www.bigmacktrucks.com/topic/41797-def-gauge-reads-empty-nox-malfunction-derate-mode/#findComment-350806 Share on other sites More sharing options...
dickbuick Posted November 3, 2016 Share Posted November 3, 2016 Same as above NOX malfunction data valid but higher than normal Quote Link to comment https://www.bigmacktrucks.com/topic/41797-def-gauge-reads-empty-nox-malfunction-derate-mode/#findComment-350845 Share on other sites More sharing options...
dickbuick Posted November 8, 2016 Share Posted November 8, 2016 After endless testing I had the new ECM and ACM programed and problem solved Thanks Mack pro Quote Link to comment https://www.bigmacktrucks.com/topic/41797-def-gauge-reads-empty-nox-malfunction-derate-mode/#findComment-351315 Share on other sites More sharing options...
Firoz Posted February 20, 2021 Share Posted February 20, 2021 On 9/15/2015 at 1:49 PM, Challenger said: Has anyone worked on the batteries? The ACM (aftertreatment control module) power wire goes straight to the batteries. Its just a small wire terminal. Ive seen 3 trucks that had the batteries replaced and the terminal was left off. As a result the truck was in derate and the DEF tank read empty. This is the only idea I have. I got same problem but I didn’t find acm powar wire . Can anyone help me about this Quote Link to comment https://www.bigmacktrucks.com/topic/41797-def-gauge-reads-empty-nox-malfunction-derate-mode/#findComment-469348 Share on other sites More sharing options...
Firoz Posted February 22, 2021 Share Posted February 22, 2021 On 9/15/2015 at 4:46 PM, Darcy1 said: Thanks for the tips people. Problem resolved. I found a broken power wire in the ACM harness about 2ft in front of the battery box on the inside of the frame rail. I'm surprised the fuse didn't blow as it was the positive rubbed through on a cross member. Repaired wire no longer in derate. I still had to clear the engine light with VCADS PRO. Thanks again everyone. Is that wire directly connect with batteries thanks Quote Link to comment https://www.bigmacktrucks.com/topic/41797-def-gauge-reads-empty-nox-malfunction-derate-mode/#findComment-469458 Share on other sites More sharing options...
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