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SES Lights Only On Startup After O2 Sensor Failure
This is a really strange one. From my initial issue, I searched the forums, found a fix, but ever since remediating my lambda sensor issue I have not found a fix for what is going on as of lately.
Original Issue
After a year of topping off my coolant every month, I finally drummed up the courage to investigate and replace my blown head gaskets
I was also getting SES codes for the O2 sensors, so I replaced all four of them (direct Bosch replacement)
A couple of local shakedown runs and a 4hr roundtrip drive with no SES warnings proved my fix was successful!...until
Returning from that 4hr drive, I exit the highway and slowed to a stop for a red-light only to have the whole truck momentarily rough idle and shutdown
She restarted without hesitation, but was now showing SES. I keep a code reader in the center console, so I read the codes and was shown as many as 12 various codes, all related to O2 sensor malfunctions, MAF input, and various shorts:
P0102: Mass Air Flow (MAF) circuit low input
P0134: O2 Sensor No Activity Detected (Bank 1, Sensor 1)
P0414: Secondary Air Injection System Switching Valve “A” Circuit Shorted
P0445: Evaporative Emission System Purge Control Valve Circuit Shorted
P0448: Evaporative Emission System Vent Control Circuit Shorted
P1451: Evap Emission Control Sys Vent Control Valve Circuit
P1482: No DTC definition found. See service manual (DMTL Heater power stageDrive cycle A:Signal out of range - below minimum)
P1884: Coolant Level Sensor Short Circuit
After some research, some others have discovered that this behavior can be due to an issue with the lambda sensor wire melting or shorting somehow. I crawled under the truck to discover that I hadn't routed the bank 2 sensor 2 (downstream of cat) wire correctly, it got wrapped around the propshaft, and broke off
My exhaust was dented near the mid pipe causing a noisy exhaust leak anyway, so I dropped the cats section, moved the three "new" (read: now ~300 mile) not damaged Bosch sensors to the new Y-pipes, replaced the passenger-side downstream O2 sensor with a new one, and put everything back together. Making extra sure to keep the wiring away from any critical drivetrain components
New Issue
My new issue since this saga is that almost all of those SES codes reappear on the dashboard, but only at startup. So now, when I get ready to drive anywhere, my startup procedure is:
Start truck
Plug in code reader
Read codes (all codes from above are returned except: )
It doesn't matter how long I drive for, the codes never come back once they're cleared. But the second I turn the truck off, doesn't matter if it's for 5 seconds, 5 minutes, 5 hours, or 5 days, as soon as she starts I get the codes back
The only strange behavior I noticed is there is a little bit of power lag below 2k rpms, almost like she's not getting enough air. But I've already taken apart and cleaned the MAF sensor & connector with the appropriate MAF cleaner and electrical cleaner
I'm truly at a loss on what steps to take next. Any ideas?
Old broken O2 sensor
new exhaust
maintenance log
Last edited by joefred16; Sep 9, 2025 at 11:16 AM.
After weeks of banging my head against a wall and scouring the internet, I finally figured out that when the O2 sensor got shredded by the prop shaft it must have grounded out and blown fuse #2 in the engine bay fusebox. I took a look tonight, put in a good fuse, cleared codes and was able to perform multiple startups with NO MORE SERVICE ENGINE SOON LIGHT!
SES Lights Only On Startup After O2 Sensor Failure
