HarryBiron093 Posted March 21, 2022 Share Posted March 21, 2022 New to the form any help is appreciated. I have an 02 RD 688 with the 460. When i bought the truck it had the problem and i have chased it since. You will be going along and the tack will go to zero for a few seconds engine dies and then restarts. The local mack garage changed both speed sensors and over the winter i sent the ECM out thinking it that it might be that. I drove the truck yesterday and it still has the cut out. Other issues When you go to shut the truck off sometimes you have to turn the key back and forth a couple times before it shuts down. I have checked the wiring and replaced the key switch hoping to fix the issue with no success. Not sure if the 2 are related or not but any thoughts on this issue is appreciated. When you plug into the truck it had/has a code for the pyrometer. But there isn't an engine light on the dash. Mack said the bulb was missing but i pulled the dash and its a sealed unit Quote Link to comment Share on other sites More sharing options...
JoeH Posted March 22, 2022 Share Posted March 22, 2022 If you're engine light is working it will power on for a few seconds then go out, assuming there's no active fault. Should look like a lightning bolt. You should have two fuse boxes, one in the glove box the other under the hood. Fire up the truck, look for the fuse that says EECU, wiggle it. I bet your engine will shut down. You'll need to pull that fuse/circuit breaker and squeeze the terminals a little tighter so they get a better grip. 1 Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted March 22, 2022 Share Posted March 22, 2022 in the box under the hood is the fuse for the ecm. #40 or 41... typically in the middle of the middle row. there is also an accessory relay next to the fuse panel in the cab, it looks like a black square cube, I dont remember the # of the socket.. when you say speed sensor's, do you mean the crankshaft and the cam sensor's? jojo Quote Link to comment Share on other sites More sharing options...
HarryBiron093 Posted March 22, 2022 Author Share Posted March 22, 2022 Joey Mack this was the repair bill from the sensors. He told me they put the rear and front speed sensors in, nothing related to the cam or crank to my knowledge. I will check those fuses ! Thanks all Quote Link to comment Share on other sites More sharing options...
Onyx610 Posted March 22, 2022 Share Posted March 22, 2022 Engine position sensor is a cam sensor, Engine speed sensor is at the flywheel housing, and vehicle speed sensor is at a tone ring on the output shaft of the trans. 1 1 Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted March 22, 2022 Share Posted March 22, 2022 the fluctuation at idle, may be the fuel pressure regulator.. I cant tell if one was installed, also did you have a 3-2 or 3-4 code? jojo Quote Link to comment Share on other sites More sharing options...
Onyx610 Posted March 22, 2022 Share Posted March 22, 2022 Also for the running “ok” and idle surge have someone check the fuel pressure. Was common for the etechs to have the plastic gear in the fuel pump strip and spin on the shaft. Also fuel pressure regulator like Joey said. Quote Link to comment Share on other sites More sharing options...
Vmac3 Posted March 23, 2022 Share Posted March 23, 2022 Would be nice to see what codes are in this. May have a J1939 issue. I know when J1939 is lost, the truck will not shut of immediately and will take 5 seconds to shut down. Never had a TPS cause an idle surge when the engine is cold. Usually if the tps is lost, the engine will default to 900rpm. The fuel system should not be checked at idle only, this should have been road tested under load with a manual gauge in the fuel system and then readings taken. That would have given you a more accurate reading. We really don't know if the fuel system is at fault still. Check to see if there is a rectangular connector on the driver side on top of the transmission, if it does run the truck and wiggle that connector and see if you notice a change in the engine. If it does then pull that connector apart, clean it with contact cleaner and put a zip tie around it nice and tight. Let us know what you find. V 2 Quote Link to comment Share on other sites More sharing options...
HarryBiron093 Posted March 23, 2022 Author Share Posted March 23, 2022 I checked the ECU fuse and wiggled per Joe H with no luck of killing the engine. See below in the video with no engine light coming on. The idle surge is no longer as issue but thanks for all the input it just needed a set of filters. The big problem is the truck dying out while driving and then coming back to life. Since to lighting bolt isn’t currently available I don’t have another way to check codes do I ? V Mac3 I don’t seem to find this connector any other descriptors ? IMG_5520.MOV Quote Link to comment Share on other sites More sharing options...
Onyx610 Posted March 23, 2022 Share Posted March 23, 2022 That connector V is talking about is on top of the bell housing. You may be able to sneak your hand up there. If not take the passenger side floor out. Quote Link to comment Share on other sites More sharing options...
JoeH Posted March 24, 2022 Share Posted March 24, 2022 On 3/21/2022 at 12:14 PM, HarryBiron093 said: New to the form any help is appreciated. I have an 02 RD 688 with the 460. When i bought the truck it had the problem and i have chased it since. You will be going along and the tack will go to zero for a few seconds engine dies and then restarts. The local mack garage changed both speed sensors and over the winter i sent the ECM out thinking it that it might be that. I drove the truck yesterday and it still has the cut out. Other issues When you go to shut the truck off sometimes you have to turn the key back and forth a couple times before it shuts down. I have checked the wiring and replaced the key switch hoping to fix the issue with no success. Not sure if the 2 are related or not but any thoughts on this issue is appreciated. When you plug into the truck it had/has a code for the pyrometer. But there isn't an engine light on the dash. Mack said the bulb was missing but i pulled the dash and its a sealed unit Does the new key switch still need a couple key cycles to get it to shut down sometimes? That seems strange, possible short circuiting in a wire harness? Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted March 24, 2022 Share Posted March 24, 2022 good call JoeH... I also thought the accessory relay was sticking, but you have a good 'Q' jojo Quote Link to comment Share on other sites More sharing options...
HarryBiron093 Posted March 24, 2022 Author Share Posted March 24, 2022 Yes the key switch will work the first time and then it will take 3 cycles sometimes. Quote Link to comment Share on other sites More sharing options...
HarryBiron093 Posted March 24, 2022 Author Share Posted March 24, 2022 What does the connector end up going to so I know it’s the right one ? Quote Link to comment Share on other sites More sharing options...
Onyx610 Posted March 24, 2022 Share Posted March 24, 2022 (edited) so here is two different pics of that plug at different angles. It’s got a metal bracket around it and is mounted on top of the trans by one of the bellhousing bolts. Did you happen to have any work/transmission work done to this truck before this problem started? Edited March 24, 2022 by Onyx610 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.