AEM Tru Boost Gauge Stuck at Max
 

I've been using the AEM Tru Boost gauge for several years without issue. When I started the car this morning though, it immediately showed max pressure (29.5) and does not change. It shows the same with the engine off.

I considered boost leaks etc, but I double checked the data in Torque, which is showing 100% normal boost and vacuum. Car also drives normally, no CEL, no other indication of anything wrong.

Has anyone seen a similar malfunction from these gauges?

Sounds like it came unplugged from the sensor, did you check the connection?

I dug into this and ended up with more questions than answers.

The gauge manual says the red and black wires should connect to the solenoid. Fairly straightforward, but as far as I can tell, it was never hooked up that way. In fact, five years ago a local shop temporarily had the solenoid connected to my evaporative purge circuit. This caused some issues, and it's been unplugged since then.

The red and black wires were tucked down by my intercooler (passenger side piping). It took a small tug to dislodge them, but it doesn't look like they were connected to anything down there. If they were, I can't imagine what.

One way or the other, the gauge was definitely functioning without those wires connected to the solenoid. The fused power, ground, and vacuum line are the only things connected to it. I'm not sure how this could be the case, or why it would stop functioning.

Ok, so the connection between the solenoid and gauge allows the gauge to control the boost. Feels silly knowing how long I've had this disconnected, but I haven't been inclined to use my lower boost map anyway, so whatever.

That's one mystery solved, but now I'm back to square one. I still have no idea what could cause the gauge to be stuck at 29.5.

AEM's best analysis was that the internal pressure sensor had failed. Sadly, this gauge is discontinued, and AEM couldn't send me the updated version without the full package (solenoid etc). That puts me $300 out for a new gauge, but at least it's working again.

The most telling symptom was that the gauge was showing a specific pressure reading even with the engine off. For anyone else in this situation, it probably means your gauge has failed.