Encountering a no RPM reading, prolonged cranking times, and misfires in your Chevy Silverado can be a frustrating experience. This case study dives into the diagnostic journey of a 2013 Chevy Silverado exhibiting these exact symptoms, offering insights that are highly relevant for owners of 2008 Chevy Silverado models and anyone utilizing a scan tool for vehicle diagnostics. While the vehicle in question is a 2013 model, the diagnostic principles and the role of a scan tool remain consistent, making this information valuable for troubleshooting similar issues in a 2008 Chevy Silverado using a scan tool.
The vehicle, a 2013 Chevy Silverado 1500 4×4 Z71 with a 5.3L engine, presented with a concerning combination of issues: extended crank times before starting, a complete absence of RPM readings on the dashboard, and misfires specifically on cylinders 3 and 8. The initial approach focused on tackling the no RPM and long crank issues first, setting aside the misfires temporarily. It was noted that while the coils were suspected, swapping them with known good coils yielded no improvement. Compression tests for cylinders 3 and 8 were healthy, registering just under 160psi, and a noid light test indicated that the fuel injectors were being commanded to fire.
Prior to this diagnostic session, several new components had already been installed: an AC Delco starter, crank and cam sensors, and a new harness for the cam sensor, suggesting a possible front seal replacement given the new timing cover. Despite these replacements, the problems persisted.
Utilizing an Autel scan tool, the diagnostic process began by observing the RPM readings. Intriguingly, while most engine menus within the scan tool reported no RPM signal, drilling down into the ignition submenu and specifically checking the crank sensor data revealed an RPM reading. This crucial piece of information confirmed that the crank sensor was indeed providing a signal to the Powertrain Control Module (PCM).
With the crank sensor seemingly functional, the next step involved meticulously verifying the wiring and terminal integrity from the crank sensor to the PCM. No issues were found – the wiring was sound, and the pins and terminals were in good condition. The same rigorous process was applied to the cam sensor wiring, especially given the new harness. Again, no faults were detected: pins and terminals were secure, corrosion-free, and continuity was confirmed with a test light. Notably, both the crank and cam sensor wiring converged at the X2 connector.
Further investigation included a thorough examination of the fuse block. It was removed to inspect the rear terminals and sockets for any signs of corrosion, burnt or bent pins. Everything appeared to be in order, eliminating the fuse block as an obvious culprit.
The scan tool also proved valuable in verifying the 5V reference circuits. According to the scan tool readings, both 5V Ref-1 and 5V Ref-2 circuits were operating correctly, showing 5V readings, thus ruling out any major shorts to ground or power issues within these circuits.
At this stage, a key question emerged regarding the RPM signal path. While it’s understood that the PCM transmits an RPM signal to the instrument cluster, the query is whether the Diagnostic Link Connector (DLC) receives its RPM data via the cluster module or directly from the PCM. Understanding the precise signal flow is crucial for pinpointing the breakdown in communication.
Research revealed forum discussions suggesting that the crank sensor primarily provides timing information for cylinder #1, while the cam sensor handles timing for cylinders 2-8. However, this information required further verification against official documentation to confirm its accuracy.
This diagnostic journey highlights the systematic approach required when troubleshooting complex automotive issues. The effective use of a scan tool, like those compatible with the 2008 Chevy Silverado, is paramount in isolating potential problems. While this case study is ongoing, it serves as a valuable reference for anyone facing similar no RPM, long crank, and misfire symptoms in their Chevy Silverado, particularly models around 2008 and onwards, emphasizing the critical role of a scan tool in modern vehicle diagnostics.
