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Guy's I'm looking for some help here and FAST! I'm an Owner/Operator of a 2003 RB688S Dumptruck. The truck does not have any power to it. I have an "Electrical Malfuntion light on the dash.

I called the dealer and they walked me thru how to read a code. I followed the Instrutions they gave me. The truck is showing a 4-1 code.

Per the dealer i replaced the speed sensor's Bellhousing and the front of the motor.

We found a broken gear on the Fuel supply pump so we replaced that too. After running the truck we checked the status of the Fuel filters and found that the Main fuel filter is only 3/4 full and the secondary filter is full (Metric spin on filter's)

The light is still on and the truck still has little power.

The air filter is brand new and the oil is in the full range and the Radiator fluid level is fine.

Please lets put our heads together to figure this out PLEASE.

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Yes Im still getting the 4-1 code.

I forgot to mention the speedo was all over the map...But it only did that one time. the dealer asked if I did a recent Clutch job? The clutch is fine.

4-1 fault code is for the speedometer, not the engine position (camshaft) of engine speed (flywheel) sensors. Typically this code is set to derate the engine when there is no signal from the sensor (as a tamper detection preventative). With Mack transmissions, a sudden occurenece, in my experience, is related to a synchronizer failure. Remove the speedometer sensor fromthe output bearing cover & inspect it for debris & damage. Install the sensor as follows: screw all the way in, back out 1 turn, tighten jam nut to no more than 15 lb ft. If the nut is over tightened the sensor can crack, probably why they asked if you had replaced the clutch recently.

"Mebbe I'm too ugly and stupid to give up!"

4-1 fault code is for the speedometer, not the engine position (camshaft) of engine speed (flywheel) sensors. Typically this code is set to derate the engine when there is no signal from the sensor (as a tamper detection preventative). With Mack transmissions, a sudden occurenece, in my experience, is related to a synchronizer failure. Remove the speedometer sensor fromthe output bearing cover & inspect it for debris & damage. Install the sensor as follows: screw all the way in, back out 1 turn, tighten jam nut to no more than 15 lb ft. If the nut is over tightened the sensor can crack, probably why they asked if you had replaced the clutch recently.

That sounds like good information were gonna try that route. I did have L.E.D. warning lights installed on the mirror arms and the dump body so im wondering if when he had the dash apart that sensor got screwed up. The guy who put the lights in the truck is not a shoemaker he works for Whelen lighting so im sure it was just a mistake or maybe it got damaged from wear and tear. Ok I'm gonna try that I'll let you know how I made out.

Thanks so far.

That sounds like good information were gonna try that route. I did have L.E.D. warning lights installed on the mirror arms and the dump body so im wondering if when he had the dash apart that sensor got screwed up. The guy who put the lights in the truck is not a shoemaker he works for Whelen lighting so im sure it was just a mistake or maybe it got damaged from wear and tear. Ok I'm gonna try that I'll let you know how I made out.

Thanks so far.

It just dawned on me that a 3 months ago the speedometer light died which is anoying cause I can't read my trip miles very easy???...

It just dawned on me that a 3 months ago the speedometer light died which is anoying cause I can't read my trip miles very easy???...

hasler brings up a good point on the back section of the trans! also Check to make sure the yoke bolt is tight as well these come loose from time to time!!

Installation of lights should not have had an effect on the speddometer, the circuit that reads the speedometer is separate from the circuit for the dash lights. The lights should be on circuit #3, the speedometer has no circuit number as it is a direct input to the vehicle ecu.

"Mebbe I'm too ugly and stupid to give up!"

Installation of lights should not have had an effect on the speddometer, the circuit that reads the speedometer is separate from the circuit for the dash lights. The lights should be on circuit #3, the speedometer has no circuit number as it is a direct input to the vehicle ecu.

Im just wondering if when the dash was apart if the speedo sensor got damaged.I'm not at all familar with the dash components.

As far as my speedometer light that light is on circuit #3. How do I check the curcuit??

Im just wondering if when the dash was apart if the speedo sensor got damaged.I'm not at all familar with the dash components.

As far as my speedometer light that light is on circuit #3. How do I check the curcuit??

The sensor for the speedometer is on the transmission, not the dash. The 4-1 code will not set if there is a problem in the dash since that is a different circuit from the speedometer. Remove the sensor from the output shaft bearing cover on the rear of the transmission and check the sensor for damage.

Circuit #3 powers dash & marker lamps. If your other dash lamps and marker/running lamps are operational it's probably just the bulb. I believe your truck should have a small solid state rectangular telltale between the speedometer guage & the tachometer guage. If it's damaged you'll probably need to change it.

"Mebbe I'm too ugly and stupid to give up!"

The sensor for the speedometer is on the transmission, not the dash. The 4-1 code will not set if there is a problem in the dash since that is a different circuit from the speedometer. Remove the sensor from the output shaft bearing cover on the rear of the transmission and check the sensor for damage.

Circuit #3 powers dash & marker lamps. If your other dash lamps and marker/running lamps are operational it's probably just the bulb. I believe your truck should have a small solid state rectangular telltale between the speedometer guage & the tachometer guage. If it's damaged you'll probably need to change it.

The sensor is on the tranny ok ok I'm sure the mechnic must know where it is. I explained to him what advise you gave me he said he would check that now in about an hour from now, I'll just explain to him it's on the tranny unless he knows that already.

4-1 fault code is for the speedometer, not the engine position (camshaft) of engine speed (flywheel) sensors. Typically this code is set to derate the engine when there is no signal from the sensor (as a tamper detection preventative). With Mack transmissions, a sudden occurenece, in my experience, is related to a synchronizer failure. Remove the speedometer sensor fromthe output bearing cover & inspect it for debris & damage. Install the sensor as follows: screw all the way in, back out 1 turn, tighten jam nut to no more than 15 lb ft. If the nut is over tightened the sensor can crack, probably why they asked if you had replaced the clutch recently.

TRUCKNUT YOUR THE MAN BABY!!!!! You hit the nail right on the head. The speedometer sensor was the problem it was melted I went to the dealer they gave me a new one and the light is off and she runs good.

Now if i can only make up the work I missed for 6 day's.

Thanks again.

Mark

TRUCKNUT YOUR THE MAN BABY!!!!! You hit the nail right on the head. The speedometer sensor was the problem it was melted I went to the dealer they gave me a new one and the light is off and she runs good.

Now if i can only make up the work I missed for 6 day's.

Thanks again.

Mark

You may want to take it to a Mack dealership and have them turn off the parameter that detects tampering with the speedometer sensor so that the truck doesn't derate for the same problem in the future

"Mebbe I'm too ugly and stupid to give up!"

I had the exact same thing happen on a 96 CL a few years ago.

The speedo sensor had a physical encounter with the trans output shaft, sensor was wiped out, and the E7 427 then derated because of no speedo signal.

The 427 felt like a END 673 170 HP motor at that point.

Replaced the sensor, and all was well again, until the range shift setup exploded a while after that.

Yes, it was a Mack T2130 trans, those transmissions have a genetic predisposition to range shift failure.

.

"If You Can't Shift It Smoothly, You Shouldn't Be Driving It"

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