Keep on Truckin'!

 

 

Big Jake Clayworth has been driving trucks for just this side of 30 years. He gets up about 5 am, gets some coffee at the truck stop, walks around his rig to inspect the tractor and trailer and then does his logbooks. He checks the road conditions and weather and then it's on the road for him. He might do a drop and hook or a live-load or maybe a live-unload. He's worked for a few of the major trucking companies out there.

They put Jake into a Peterbilt 386 with Cummins ISX CM871. "It started acting up two weeks ago," Jake told me, "It cranked but wouldn't start. Fan clutch solenoids would cycle on and off with the key on and the lift pump was making noise."

Basically, how this system works is that sensor inputs are fed into the chassis node where the info is processed and delivered to the CECU by way of the CAN data bus. The chassis node also controls various relays (trailer turn signals, stop lights, backup alarm, turn signals--you get the idea).

"I made the mistake of taking my rig to a real hack," Jake said. He smoked some computers and wires."

"Have you tried Smokey's Wire and Component Smoke?" I asked, but Jake wasn't in the mood for joking.

"I get paid 43 cents a mile--those are paid miles." What Jake meant was that they weren't" practical miles." It's miles paid "how the crow flies." He wasn't getting paid for down time.

 

Whoever replaced the chassis node on this truck didn't follow procedure, for one. You have to disconnect the batteries while replacing a chassis node. You should only reconnect the batteries after everything is reconnected. You also need to simultaneously supply power to the new chassis node and CECU during the first power cycle or else a fault will be triggered and logged on the DIC when the CECU detects that communication of the chassis node is corrupt.

 

"You can't just cycle the ignition because the parameter file is transmitted to the chassis node only when you complete the battery power cycle," I said. You have to cycle battery power directly at the batteries. Disconnect battery power for about a minute during the power cycle to allow power-down.  On a J-1939 backbone, DTC's consist of a Source Address (SA) identifying the ECU sending the code (SA0 = Engine ECU #1), a Suspect Parameter Number (SPN) which identifies the PID fault code error message and a Failure Mode Identifier (FMI) identifying the type of fault. Jake's Peterbilt was loaded with codes.

 

I turned the key ON, started the ESA and established communication with the vehicle while Jake watched. His Zero-dollar-clock was ticking fast and he reminded me of it.

 

"I need a drink of Doctor Knucklebuster's Diagnostic Liquid to help me out here, Jake."

"Considering what I'm paying you, you should be able to by a solid gold magic wand, you think?"

 

"Ouch." Jake wasn't a happy camper. He was plagued by Pavement Princesses bothering him at the last truck stop. "I know that Lot Lizards are earning a living, but geez, they are getting worse," Jake tells me. "That Sleeper Leaper was busier than a cat covering crap on a marble floor."

 

Okay, Jake--I found a DTC 148309 stored--which tells me that CECU can't read messages from the engine on V-CAN,"  I said.

 

"Which means what?" Jake asked.

 

"You could have an open or a short in the wiring from the CECU to the engine ECU. You might have a terminating resistor issue," I said.

 

"Well, that would make a bishop mad enough to kick in stained glass windows," Jake said.

 

I did some rapid-fire diagnostics and won't bore you with the details, but I found an issue at the Steering Angle Sensor (SAS). This Peterbilt uses a Meritor Wabco SAS that is SUPPOSED to have a jumper wire between terminals #2 and #3 that connects CAN Low to CAN high. The terminal at Pin #3 had poor tension. After that, and a few other checks and repairs, I did the SAS calibration procedure with my Meritor Wabco Toolbox software on my Toughbook. By the way, the terminator value in the SAS is 180 Ohms.

 

"All fixed, Jake. I had to replace some wiring from nasty wiring repairs that hack did, but you are good to go."

"You know, when the Lord was handin' out brains, that fool thought God said trains, an' he passed 'cause he don't like to travel."

 He showed me another truck to work on. "This one's an old Pete 379 with a Detroit S60. The hack said he couldn't find anything wrong with it."

This Peterbilt had an ECM and a cab-mounted, Wabco ABS ECU. I measured 131 ohms on the data link. The terminator near the left hand cab mount had been eaten alive by corrosion. I replaced it, installed a sacrificial anode and measured the resistance of the parallel terminators: 62.2 ohms.

 

Jake was thrilled until I handed over my bill. "No offense, Bob, but I hope I don't see you again for a while."

"None taken, Jake. Watch out for those lot lizards."