P135B on Chevrolet: How to Diagnose & Fix
Ignition Coil Supply Voltage Circuit Bank 2
1 Chevrolet model · 1 documented issue · 1 critical · $150-$900 repair
P135B on Chevrolet by model: symptoms, diagnosis and fix
Many second-gen Traverse owners experience random no-crank / no-start events, sometimes after the engine shuts off while driving. GM service bulletins identify two patterns: bent or backed-out terminals at body connector X203 causing loss of communication on the HSLAN data bus with multiple stored DTCs, and a separate intermittent no-crank condition on certain 2019 3.6L LFY models built before February 22, 2019, flagged by ignition coil supply and ignition relay feedback codes and caused by loose terminal tension in the underhood fuse block. The result is being stranded with a vehicle that will not respond to the start button.
Common Symptoms
- Intermittent no-crank when pressing start
- Engine shuts off while driving then won't restart
- Multiple unrelated warning lights / loss of communication
- Sometimes restarts after sitting
How to Fix
Have a technician scan for HSLAN/loss-of-communication DTCs and inspect/repair connector X203 for bent or damaged terminals per the GM bulletin; the second bulletin (19-NA-119) addresses the no-crank codes by voltage-drop testing the underhood fuse block (X50A), repairing loose terminals, and replacing the fuse block if the drop exceeds specification. Owners should also rule out the simpler offenders first — loose/corroded battery terminals, a weak main battery, and a dead key-fob battery, all of which mimic the same symptom.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
Sources for this issue (2)
P135B code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P135B mean on a Chevrolet?
P135B stands for "Ignition Coil Supply Voltage Circuit Bank 2." Manufacturer-specific (General Motors — Buick, Cadillac, Chevrolet, GMC). Each cylinder has its own ignition coil, and the engine control module monitors the battery-voltage feed running from the fuse to the bank 2 coils. This code sets when the ECM detects less than about 2.5 volts on that supply circuit. With no voltage to the coils, the cylinders on that bank cannot fire, so the engine misfires badly, runs rough, loses power, and may not start. Note that BMW and MINI use P135B for an implausible knock sensor 2 signal instead, so confirm the definition against your make. On Chevrolet it is documented across 1 model: Traverse.
What are the most common causes of P135B?
The most common causes of P135B are: Blown ignition coil fuse for bank 2, Short to ground in the ignition voltage supply circuit, Open or high resistance in the coil power feed or a corroded connector, Failed ignition coil on bank 2 shorting the supply, Damaged or chafed engine harness near the valve cover, Faulty engine control module (rare — verify circuits first). The specific cause varies by vehicle.
How much does it cost to fix P135B on a Chevrolet?
Published repair estimates on Chevrolet range from $150 to $900 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.