Generally, a vehicle’s onboard diagnostic system must be brought back into “normal” function in order to clear a permanent diagnostic trouble code. That means the DTCs triggering malfunction indicator lights in association with an engine seizure should still be readable prior to repair/replacement. There may also be pending codes (think of them as “maybe” codes) and historical codes to track down.
Those codes represent problems that have either been repaired or that the onboard diagnostic system doesn’t consider necessary to address immediately. They can provide powerful clues as to what’s really going on with an engine.
It isn’t necessary to run the engine to use an OBD II scanner. Turning the key to the “on” position is enough. So, if the automotive maintenance facility manager (from the first part of this two-part column) takes a good scanner to inspect the customer’s seized engine, they can still read what the onboard system registered about the powertrain between the last scan/clearing event and the seizure (i.e., a seized engine doesn’t stop the battery from powering the radio or the onboard computer, etc.) The manager’s scanner may also be able to detect pending or historical codes.
In an excessive oil consumption case with a seized engine, you might see the following DTCs.
Generic codes:
· P0300-P0308: random/multiple cylinder misfires (caused by lack of lubrication and increased friction)
· P0520: engine oil pressure sensor/switch circuit malfunction (low oil pressure due to insufficient oil)
Manufacturer-specific codes:
· (Hyundai/Kia): P1511 (excessive engine oil temperature), P1523 (oil control valve stuck open)
· (Ford): P06DD (engine oil pressure control circuit stuck off), P06DE (engine oil pressure control circuit low)
· (GM): P0521 (engine oil pressure sensor/switch range/performance)
Before the engine seized, you might see a pattern of the DTCs listed below.
Generic codes:
· P0420, P0430: catalyst system efficiency below threshold (oil burning can damage the catalytic converter)
· P0365-P0369: camshaft position sensor issues (oil leaks can damage the sensor or wiring)
· P0505: idle air control system malfunction (oil contamination can affect idle control)
Manufacturer-specific codes:
· (Hyundai/Kia): P1326 (engine knock sensor detection system); (engine knock due to low oil pressure)
· (Ford): P0523 (engine oil pressure sensor/switch circuit high)
· (GM): P1514 (engine oil pressure too low)
Contrast the before and after DTC picture above with the same alleged cause of engine seizure, except the DTCs include an additional array of rod knock-related codes before and at seizure: P0325, P0326, P0327, P0328 (knock sensor circuit malfunction), P0011, P0012, P0016, P0017 (camshaft position; irregular timing), and P0335-P0349 (crankshaft position sensor issues).
That would tend to indicate a different problem with the engine, such as a rod bearing clearance defect allowing engine oil to bypass into the combustion chamber.
Unfortunately, automakers aren’t required to give OBD II systems a permanent record of DTCs during the life of the vehicle. Much of the DTC information can be cleared by experienced technicians, especially if they have access to OEM diagnostic systems.
That is why routine scans taken before going to an OEM dealer to check MILs can be critical in later debunking an “inadequate maintenance” or negligent service allegation when an engine fails. It is also why scanning the OBD II system for alleged service-related engine problems should be done right away. Once an engine is replaced, the prior DTCs can be cleared.
It's true that OBD II system diagnostics can be complex and ultimately require ASE-trained analysis to chase the DTCs, pending codes, and symptoms all the way down the rabbit hole.
However, if the customer has no scan records and the independent automotive service facility doesn’t at least scan the OBD II system after-the-fact, then there may be no way to challenge an OEM’s claim of “inadequate maintenance” or negligent service short of a complete teardown, and even that may not provide an evidentiary slam dunk. Showing a rod finally broke is not the same as demonstrating the engine registered long-term symptoms associated with incorrect connecting rod bearing clearance.
For anyone who hasn’t yet explored scan tools, now is the time to get educated. They aren’t just for hardcore repair shops anymore.
The rapid increase in engine defects and warranty denials means that professionals in the automotive service industry must understand how to investigate claims potentially involving engine defects, which includes capturing DTC information. There is no longer any way around it. Whoever controls the DTCs controls the narrative.
