What does this OBD II code mean?
This generic OBD2 code is set when the Powertrain Control Module (PCM) senses a problem in the control circuit of the deactivation valve for cylinder #4.
Why does this OBD II code appear?
Modern “V” type engines, especially V8 engines, implement a strategy known as “cylinder deactivation” to enhance fuel economy. The principle is quite simple, under certain light load conditions the PCM temporarily deactivates up to 4 cylinders, imagine it as a virtual V4 engine. In order to accomplish this functionality, the engine is equipped with variable timing solenoids on the exhaust valves. Depending on the engine firing order the manufacturers configure the system to operate in a way that the driver doesn’t notice any change between modes.
Since the PCM is constantly monitoring each exhaust valve control circuit voltage and/or current, any abnormality is noticed immediately.
The OBD2 code P3470 is stored in memory when the PCM detects a problem in the control circuit of cylinder 9.
What symptoms may occur with this OBD II code?
Expect the typical symptoms from a P3470 condition:
- CEL lit. The Check Engine Light will turn on after few driving cycles to alert the driver about the situation.
- Poor fuel economy.
- Possible misfires and/or spark knock.
What are the causes that trigger this OBD II code?
There're many factors that could cause a P3470 condition including among others the following:
- Damaged, burnt, corroded, open or shorted solenoid wiring.
- Worn, corroded, burnt, disconnected or bent wiring harness connector pins.
- Low engine oil level
- Low engine oil pressure
- Clogged oil passage or engine mechanical condition
- Faulty, deficient variable timing solenoid
- Even when unlikely, a defective PCM cannot be discarded.
Diagnostic strategy for troubleshooting this OBD II code
It's highly recommended starting the diagnostic process with the usual information gathering:
- With the help of a professional OBD2 scan tool, preferably one with OEM capabilities, take note of all data trouble codes in memory, including pending codes.
- Take note of freeze frame information (if present).
- Query the vehicle owner about what, when and where the failure occurs. Does it happen with the engine hot? Cold? Under load? All the standard questions.
- Take note of the vehicle VIN and find a reliable source of technical reference.
Once you are done, the next step is discarding an intermittent condition.
- Using your scan tool clear DTC memory.
- Perform a complete driving cycle according to OEM procedures.
If the code P3470 disappears then inform the owner about the intermittent nature of the code and explain that further testing with the code present will be required. If the code does appear then continue to the testing stage, consisting in discarding the possible causes of the problem.
IMPORTANT: the diagnostic procedure explained in this section should be taken as a guideline. Always refer to specific OEM procedures when possible.
The workflow for the diagnostic process is:
- The tests should be executed in sequential order, in other words, complete step 1 before going to step 2 and so on.
- Repair, fix, or replace any component if you suspect is not in good condition.
- If any repair, fix, reprogramming or component replacement is made during any step then you should clear DTC memory and repeat the whole KOER driving cycle.
- If the DTC appear again then you should continue to the next step.
- If the DTC does not appear again after completing the KOER tests then you can assume the problem is fixed, in that case, continuing with the remaining steps would be optional.
The diagnostic process for the code P3470 is as follows:
- Engine Oil Level and Condition: Verify engine oil condition and level. Perform a complete oil service if necessary.
- Engine Oil Pressure: using the adequate adapter and engine oil gauge, perform an engine oil pressure test. Refer to the appropriate literature to check results. In order to continue the diagnostic process, you will need to fix any issue in the engine oil system.
- Variable Timing Solenoid harness wiring and connector: carry out an exhaustive visual inspection of solenoid wiring and connectors. Pay special attention to burnt, corroded, open, shorted to ground or deteriorated wiring and/or connector. Unplug the solenoid and check for corrosion, damage, bent pins, etc.
- Electrical tests: with the help of a digital volt-ohm meter (DVOM) and the adequate wiring diagram perform a KOEO and KOER check on the solenoid. Verify supply and/or reference voltage, electrical resistance, continuity, current and ground integrity. Compare the obtained values with the appropriate OEM literature.
- Solenoid functional test: some manufacturers include built-in tests that help in the process of diagnosing the variable timing system, others not. Refer to the proper literature in order to perform a complete system diagnostic. The test allows you to manipulate the solenoids activation.
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Problems with the powertrain control module: the most unlikely cause for this code is a faulty PCM or a corrupted program. Yet, if you are completely certain that all prior tests passed then you must remove the PCM and check it, reprogram it or replace it as necessary.
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