Fault Code P1516

[Robert Wright]

I have been trying to smooth out a minor lump in the idle of my 1999 C2. Have done plenty of work lately to include replacing plugs, coils, AOS (gee, that was fun!), cleaned the TB and ICV. Runs like new now but still have a very minor rough idle. Using my Durametric I now have a reoccuring code P1516, DVE Control Range.

Does anyone know exactly what this code is and could it have anything to do with the rough idle.

Thanks in advance for any suggestions or thoughts.

[Loren]

P1516 Intake Manifold Switchover 1 (Output Stage) - Open Circuit

"Function

An intake air system divided by a tuning flap permits the oscillations of the intake air column to be exploited over a large engine speed range (resonance supercharging). During this process, the different power strokes mean that air is sucked up between the cylinders from both reservoirs of the intake air system in alternation. This alternating suction excites the air mass in the intake air system. During resonance, the intake frequency of a cylinder bank corresponds with the natural frequency of compressive oscillations in the associated reservoir. The natural frequency is determined by the geometry of the intake manifolds, resonance pipes and reservoirs. A decisive factor, however, is the overall length of the pipes from one intake cylinder to the next, the different lengths of intake and resonance pipe sections and the depth of the reservoir in the direction of flow.

The DME control module activates a change-over valve which opens and shuts the tuning flap through vacuum. The tuning flap is open without flow, but is actuated and closed each time the ignition is switched on. Once the engine reaches the programmed idle speed after start-up, the tuning flap is opened once more.

Switching points of the tuning flap:

Tuning flap not actuated from 700 to 3120 rpm and from 5120 rpm.

Tuning flap actuated from 3120 to 5120 rpm, if the throttle is also more than 30 % open at the same time."

Possible causes:

- Change-over valve (coil) open circuit.

- Open circuit in wiring.

- DME control module

Rough idle may be related but is likely related to a dirty/stuck idle control valve (ICV) and/or dirty throttle body. Definitely check that too. Both have been covered here in some detail.

[Robert Wright]

Loren,

Wow..... interesting information, thanks very much. I will get a real good look again at the throttle body and ICV.