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General Smog Check

What Causes a P0012 Trouble Code? Camshaft Timing Retarded

Hello. What does an OBD-II Trouble Code P0012 mean? Is this something I can fix myself? Thanks.


OBD-II P0012 Trouble Code

P0012 OBD-II Trouble Code: Camshaft Position A - Timing Over-Retarded (Bank 1)

Here is what a P0012 means...

P0012 is an OBD-II generic trouble code which indicates a vehicle's ECM (engine control module) has detected the intake camshaft timing on Bank 1 (number 1 cylinder side of engine) does not correspond with the intake camshaft timing (in degrees) which the ECM expected to find; the camshaft timing is over-retarded, meaning the intake camshaft is opening too long after the engine's intake cycle. Diagnosis will be required to find the reason for the P0012 trouble code. It is possible your vehicle is experiencing noticeable drivability problems and/or idle and starting issues.

What caused my vehicle to set a P0012 trouble code?

Engine valve timing is variable (on most gasoline and diesel powered vehicles on the road today), hence the term "Variable Valve Timing". What does this mean? The engine control module is able to adjust when the sparkplugs are fired, and at which precise moment the intake and exhaust valves open and close. The timing of these events very much effect the efficiency of combustion. On some engine designs, intake and exhaust camshaft timing is controlled solely by electronic components. On most others, the system is controlled by hydraulics and with the use of electronic valves to control oil flow/pressure. For those engines using a hydraulic system, it is important to ensure the engine oil is of the required viscosity, not contaminated, and of the required amount/level; as recommend by the vehicle's manufacturer.

Here are a few things which could cause the ECM to trigger a P0012 fault:

  • Contaminate engine oil (rare fault).
  • Inadequate oil flow to the variable camshaft timing (VCT) oil control valve (OCV).
  • Defective VCT oil control valve (OCV). Control valve more than likely stuck in open position.
  • Defective camshaft phaser. The camshaft phaser is the mechanical component (gear component) of the VCT system responsible for directly controlling the timing (opening/closing) of the intake and exhaust valves. The phaser is more than likely stuck in the retarded position.

What symptoms can my vehicle experience with a P0012 OBD-II trouble code?

  • Possible hard engine starting, especially during cold start.
  • Poor engine idle and/or possible stalling when stopped.
  • Illuminated check engine or malfunction indicator light/lamp.
  • Possible decrease in fuel economy.

How can I fix a P0012 problem and where should I start?

The diagnosis for this fault should begin with ensuring the engine oil and oil filter are within their respective effective use lifetime. Triggering a P0012 trouble code due to old oil is rare but certainly possible. Since this inspection is the simplest to do, check your engine oil first.

Next we'd recommend clearing the P0012 trouble code from the ECM memory using a scan tool, and watching to see if the check engine illuminates again (clearing the P0012 will extinguish the CEL/MIL light). If the light turns back on immediately after you've cleared the code and restarted the engine, you can be confident there is a mechanical fault which needs to be repaired without wait. If the light does not turn back on, then perhaps the fault was intermittent and caused by an unexpected irregular engine operating condition. Continue to drive your vehicle for at least 100 miles and over the course of a few days in order to make the "Emission Monitors" ready for the smog check as well as to ensure the check engine light does not illuminate.

If the check engine light returns and a trouble code P0012 is once again stored in the ECM, we have to recommend getting a diagnosis from a reputable smog repair station. Diagnosing a P0012 trouble code requires specialized tools and specific knowledge of engine emissions; which we'd rather not go into it in detail here since it requires extensive repair and diagnosis knowledge and misdiagnosis will most certainly results in monies spent unnecessarily, or worse, greater engine damage.

  • Clear trouble code from ECM and check to see if the check engine light or MIL turns on again.
  • Check engine oil for proper viscosity and level.
  • Check/replace oil filter is passed its operational lifetime.
  • Check/replace bank 1 intake valve camshaft oil control valve.
  • Check/replace bank 1 intake camshaft oil control valve solenoid.
  • Check/correct timing chain position (Jumped camshaft timing chain/sprocket/skipped gear tooth).

Can I drive my vehicle with a P0012 trouble code and illuminated CEL?

  • We do not recommend driving your vehicle with a P0012 trouble code. Fuel economy will be diminished, as well as your engine may show signs of hesitation and/or lack of power. Bank 1 of the engine is not running at optimum levels may unnecessarily place additional load on bank 2.
  • The check engine light or malfunction indicator lamp illuminated while P0012 is recorded in the ECM.
  • Your vehicle will not be able to pass a smog check.

posted by SmogTips Support 05-22-2018 04:37 PM
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