ALLDATA Tech-Assist Helps Technician Wrangle with Disaster
One of the biggest fears in most technicians’ minds is a job that comes back. Comebacks don’t just cost the shop valuable hours; they can also damage a technician’s reputation and potentially impact their career. Still, they’re sometimes unavoidable. After all, modern vehicles are packed with advanced technology, complex wiring, and the occasional gremlin that comes with it.
It can be incredibly frustrating for the customer, who’s once again without their vehicle, and for the technician, who’s struggling to consistently replicate the issue. Sometimes, short of calling in a priest to exorcize the demons from the electrical system, it simply takes some deeper digging to uncover the root cause.
With the Jeep in the bay, it was time to bust out the proverbial shovel.
Dashboard Ducks
This 2018 Jeep Wrangler, equipped with a 3.6-liter V6, came off the flatbed already looking suspicious. The starter would engage, then quit mid-crank like it had somewhere better to be. Several diagnostic trouble codes (DTCs) were present, all pointing to communication issues. Not to waste time, the technician called ALLDATA’s Tech-Assist team to find where to start.
The first call with the Tech-Assist team began with a suggestion to check the star connectors behind the glove box. A few love taps with a screwdriver later, the gauge cluster settled down. The dashboard lights turned off, the DTCs cleared, and the Jeep almost seemed like it wanted to behave. The Tech-Assist team then recommended pulling the star connector apart to check for corrosion or broken solder joints—and possibly inspecting the aftermarket taillights and aluminum fender liners.
The technician disconnected modules one by one to verify their operation. Most checked out fine, but during the process, the issues returned. This time, the fuse box in the engine bay revealed the culprit that ended the technician’s search: the fuse box bolts were loose. Once properly tightened, everything returned to normal.
- U0418 - Implausible data received from brake system control module 1
- U0432 - Invalid data received from multi-axis acceleration sensor module "A"
- U0416 - Implausible data received from ESP
- U0101 - Lost communication with TCM
- U1110 - Lost vehicle speed message
- U1110A - Lost vehicle SCM-CAN-C
- U1412 - Implausible vehicle speed signal received
- U0155 - Lost communication with cluster/CCN
To button it up, the tech replaced the auxiliary battery and confirmed the DTCs stayed gone.
To the Wiring and Beyond
A few days later, the Jeep came back again. Same rollback. Same problems. Same technician developing a twitch in his left eye. The symptoms were familiar, but not as severe. The shifter was acting strange, the front and rear lights were flickering, and a new no-crank issue appeared, now showing up only when the vehicle was cold.
CAN resistance at the diagnostic port was within spec, so the tech started trying to isolate the fault. Individual components were cooled, including the star connectors, the secure gateway module, and the body control module. Still nothing. Eventually, the problem became completely random and indifferent to temperature.
A bump test on the steering column provided a temporary fix. That sent the technician down a new path. Focus shifted to the push-button start switch and the secure gateway module. Wiggling wires and reseating connectors had no effect. Another bump test fixed it again, but only for a moment.
Once again, ALLDATA Tech-Assist jumped on the line and recommended pulling the star connectors apart for a closer inspection—this time checking each one for cracks. Armed with a magnifying glass, the technician examined the circuit boards inside the modules. Sure enough, there it was: multiple cracked solder joints. The Jeep wasn’t possessed—it was just a Friday special.
The Road Goes on Forever, and the Party Never Ends
With the bad solder joints repaired, no DTCs present, and the Jeep running smoothly, the customer picked it up. And for a few short days, all was quiet.
Then the Jeep returned. But this time, it was driven in. That felt like progress.
The issue now was high fuel trims. DTCs showed both banks maxed out on the O₂ sensors. The short-term trim couldn’t compensate, and the upstream sensor was reading 0.8 to 0.9 volts—indicating a rich condition. But that didn’t align with the fuel trims. Tech-Assist advised the technician to induce a large vacuum leak to see if the sensor voltage changed. It didn’t budge.
Since the trims couldn’t go any higher, and the sensor was clearly lying, the upstream O2 sensor was replaced. The fuel adaptives were reset, trims normalized, and the Jeep finally seemed content. This time around, the fix was final, and the owner was back to “Jeep hair, don’t care” status.
- $7E8 - Short term fuel trim (bank 1)
- $7E8 - Long term fuel trim (bank 1)
- $7E8 - Short term fuel trim (bank 2)
- $7E8 - Long term fuel trim (bank 2)
- $7E8 - Oxygen sensor output voltage (bank 1 sensor 1)
- $7E8 - Oxygen sensor output voltage (bank 1 sensor 2)
- $7E8 - Oxygen sensor output voltage (bank 2 sensor 1)
- $7E8 - Oxygen sensor output voltage (bank 2 sensor 2)
Wrangled Into Submission
Electrical gremlins are the stuff of technician nightmares, right up there with warranty work and parts on national backorder. But being thorough when things get complicated is what brings customers back. Sometimes you need to step outside the diagnostic chart and trust your gut. That kind of thinking doesn’t come from textbooks or training modules.
It comes from time spent in the bays, tracking down the weird stuff no one else wants to touch. And while this Wrangler may have tried its best to earn a permanent spot in the shop, the technician came out on top, solder gun in one hand, scan tool in the other.
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