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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3304
Experience:  ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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I have a 2001 Freightliner classic xl with a Detroit 60

Customer Question

Hey I have a 2001 Freightliner classic xl with a Detroit 60 series in it. I have been on road for last 7 days. Got to truck stop tonight and went to go into opt idle and nothing
JA: Sometimes things that you think will be really complicated end up being easy to fix. The Heavy Truck Mechanic I'm going to connect you with knows all the tricks and shortcuts. Is there anything else important you think the Heavy Truck Mechanic should know?
Customer: Check engine light flashed so I took a look at oil and it was ok
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Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Jeremy replied 1 year ago.

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The truck won't run or it won't go into opti-idle?


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Customer: replied 1 year ago.
Truck will run,
Customer: replied 1 year ago.
Opt idle just won't come on,
Customer: replied 1 year ago.
When I push override switch it tells me to check engine and shut down. ?? I checked engine. I have been functioning differs items and I turned on fan and I don't hear it come on, I hear a pop sound. Unsure if this relates, pressures and temp are good
Expert:  Jeremy replied 1 year ago.

When you push the diagnostic button, can I get the flash codes on the dash from the yellow light and the red light? The flash codes are 2 digit codes.

This will help determine the fault in the system.

Expert:  Jeremy replied 1 year ago.

You turn on what fan and you get a pop sound?

Customer: replied 1 year ago.
Engine fan, 2001 Classic xl, I don't see a code number on the lights
Expert:  Jeremy replied 1 year ago.

You should always have a code. If you have no codes, they would flash a 2 and a 5 indicating 25.

If you are getting a pop sound with the fan, you might have a bad engine fan hub or one that is going bad. It could also be the solenoid acting up that supplies the lock for the fan.

At this point, since there is nothing flashing, I suggest having the engine scanned for stored codes to determine the fault with the opti-idle system. It won;t allow and engagement if the neutral switch can't be seen, the park brake switch, the clutch switch, or a stored engine code.

Some of these freightliners will reset the stored codes when you cycle the key first 5 times, and then 8 times after. A lot of dealers have turned that feature off in the parameters to drive up business for them, but there are a lot of the Calssics that still have that activated. Give that a try and see if the codes will reset and the opti-idle will come on for you.

Customer: replied 1 year ago.
Ok red shut down light 2 then 5. Yellow check engine light 6
Expert:  Jeremy replied 1 year ago.

Is there a flashing before the 6? It needs to be 2 digits.

Customer: replied 1 year ago.
After 6 on check engine yellow then 3 more flashes
Expert:  Jeremy replied 1 year ago.


PWM Drive Short to Battery or Open Circuit


You basically have a injector harness or injector issue on the electrical side. You'll need the truck scanned wit hteh Detroit software to determine which injector it is that is causing the issue.

That is why the opti-idle will not engage.

Customer: replied 1 year ago.
Can I run the truck? I have to make it back to house for my mechanic to fix
Expert:  Jeremy replied 1 year ago.

Yes, you can run the truck. It is just a pulse width issue where the pulses are getting jumbled. It's the fisrt point that the solenoid on the injector is getting worn out or there is a small short at the pin.

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