PDFT Posted August 15, 2022 Share Posted August 15, 2022 Hello, I am reaching out again for some help. I appreciate the responses I have got in the past. I have a 2018 Granite with the MP-8 engine. I am getting fault code SPN-1639 for the Fan Speed. The fan does lock up after the engine gets up to temperature, before it is at full temperature the fan works fine. What sensor is controlling the fan speed and where is it located? Any help will be appreciated! Quote Link to comment https://www.bigmacktrucks.com/topic/70288-2018-granite-mp-8-spn-1639/ Share on other sites More sharing options...
Mackpro Posted August 16, 2022 Share Posted August 16, 2022 Everything is self contained inside the fan clutch. A faulty fan clutch, worn pins in connector, wiring damage or engine ecm issues could be the cause. In some model years the fan speed sensor is powered by a 5 volt wire that also powers other 5 volt sensors like the boost pressure sensor. An issue with a totally unrelated sensor can cause a fault code for something else using the same 5 volt wire. Quote Link to comment https://www.bigmacktrucks.com/topic/70288-2018-granite-mp-8-spn-1639/#findComment-506503 Share on other sites More sharing options...
PDFT Posted August 16, 2022 Author Share Posted August 16, 2022 Thank you for the reply. I do not have any other fault codes. Do you suggest replacing the fan clutch? Quote Link to comment https://www.bigmacktrucks.com/topic/70288-2018-granite-mp-8-spn-1639/#findComment-506516 Share on other sites More sharing options...
Mackpro Posted August 16, 2022 Share Posted August 16, 2022 (edited) I’ll run the fault code through Tech Tool sometime this morning and see if there are any test that can be done before replacing fan clutch Edited August 16, 2022 by Mackpro Quote Link to comment https://www.bigmacktrucks.com/topic/70288-2018-granite-mp-8-spn-1639/#findComment-506522 Share on other sites More sharing options...
Mackpro Posted August 16, 2022 Share Posted August 16, 2022 For that year model truck in Tech Tool , all the codes are in the P***** code format. I have found no way to cross the SPN fault code format to the P code format that is now used. A lot of the time generic code readers or even the dash diag will read out codes in the older format. But when you plug up the to Tech Tool you get a totally different type of code format. Early ETECH and MP’s used the MID SID format, then around 2010 it changed to the SPN format and then around 2016 the P series fault code format came about. Very confusing of course. On your fan clutch at the electrical connector, pins 1 and 2 are a pair of twisted wires and this is fan speed signal . Pin 5 is the power to the fan speed sensor, I’m assuming it’s 5 volts. The other pins are for voltage and ground for engagement and over temp . Quote Link to comment https://www.bigmacktrucks.com/topic/70288-2018-granite-mp-8-spn-1639/#findComment-506529 Share on other sites More sharing options...
PDFT Posted August 17, 2022 Author Share Posted August 17, 2022 Thank you, I will check the pins. I have another scan tool. I will try that and see if I get P codes 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70288-2018-granite-mp-8-spn-1639/#findComment-506633 Share on other sites More sharing options...
PDFT Posted August 18, 2022 Author Share Posted August 18, 2022 I plugged in my scan tool and got no codes. I do not have a check engine light on, only the lightening bolt on the dash. I got the SPN code from my ELD. I did not have time to check the pins yet, but I had a thought, could the pressure switch in the A/C line be causing the cooling fan to lock up on high. I am thinking that because I am not getting any engine malfunction codes Quote Link to comment https://www.bigmacktrucks.com/topic/70288-2018-granite-mp-8-spn-1639/#findComment-506744 Share on other sites More sharing options...
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