P0135 P1682 P0300 Diagnosis and No Spark on Bank 1 in 2009 Chevrolet Silverado 1500

If P0135 is not currently set, the PCM may be satisfied. The code triggers when heater current exceeds 3 amps or drops below 1/4 amp on the oxygen sensor heater circuit—these values are approximate and should be verified in official service manuals. This heater circuit does not operate continuously; it activates during specific engine conditions. I’ll provide a more detailed explanation later tonight.

No spark is detected on Bank 1 at idle, though spark is present on Bank 2. I’ve checked while cranking and will verify if spark appears during startup. When I took the truck to a friend, he noted that there was no constant misfire on his scanner—only cylinder #7 showed misfire at idle, which spread to other cylinders as RPM increased. At idle with the plug connected, Bank 1 shows no spark, while Bank 2 has consistent ignition. This is valuable context for diagnosing the issue.

Each coil has four wires: red (power), black (ground), brown (signal), and a color-coded individual wire that varies per coil. I believe this signal wire connects directly to the PCM, which is critical for ignition control.

I just started the truck and it ran smoothly with no misfires. The idle is slightly unstable and the engine bogs down when I release the throttle. I’m planning to return and test again, as the vehicle typically runs intermittently before returning to Bank 1 misfiring.

As long as the engine is warm, it runs fine—this behavior doesn’t make sense. If this were a gasket or vacuum leak issue, wouldn't that affect all cylinders equally? I replaced the manifold gasket due to oil contamination in the intake. My torch wrench broke during installation, and I used carb cleaner with a smoke machine to check for leaks. The problem began before the gasket replacement, so it’s unlikely related.

If there's no spark on Bank 1, check the pink wire (common power feed) at each coil on that bank. With the key on, verify if you have battery voltage (B+) on the pink wire. Before doing this, ensure fuse 24 (20A) in the underhood fuse block is intact—this fuse powers Bank 1 coils. You previously reported a P1682 code; confirm whether it's still active.

Have you found any resolution or diagnostic results so far?

I was away for three days helping with car deliveries. Before I left, the truck ran better—no misfires—but it stutters badly when RPM drops below 1800. When stopped, fuel trims spike to +30 and idle becomes unstable. I’ve returned and am ready to retest the system.

I drove the truck all day and on my way home it began backfiring severely. To keep driving, I disconnected the Bank 1 fuel injector fuse. After that, Bank 1 coils stopped firing entirely—though each coil has proper 12V and ground connections. This suggests a potential control issue. While Ford vehicles have known issues with VCT solenoids, do Chevrolet trucks have similar systems? Any insight would be appreciated.

How did you confirm that Bank 1 coils are not firing? Is the P1682 code still present? Do you have spark at any coil on Bank 1?

Hi Joe, I finally figured it out. There was a short in the Bank 1 coil harness. While testing for ground, I noticed my test light was dim. After wiggling the wires, the light flickered on and off—indicating intermittent contact. Upon inspection, the internal prongs of the harness were bent outward, causing poor electrical connection. I realigned them and now the truck runs perfectly. I’m relieved to have resolved this issue. I hope no damage occurred during previous misfire episodes. Thank you all for your help—I feel much more confident diagnosing engine problems now.

Great to hear you found the solution!