Rpm gauge

wiram · Apr 1, 2014

Has anyone had any issues with there Rpm gauge not working properly when I come to a stop it drops all the way down to 100 rpm's according to the gauge but the truck is still running normal. I will also do this going down the highway it will drop from like 1800 to 1000. Any ideas?

Redtruck-VA · Apr 1, 2014

Here's some information from the manusl.
² Actuator Test - Each time the cluster is put
through the actuator test, the tachometer needle will
be swept to several calibration points on the gauge
scale in a prescribed sequence in order to confirm the
functionality of the gauge and the cluster control circuitry.
On vehicles with a gasoline engine, the PCM continually
monitors the crankshaft position sensor to
determine the engine speed. On vehicles with a diesel
engine, the ECM continually monitors the engine
speed sensor to determine the engine speed. The
PCM or ECM then sends the proper engine speed
messages to the instrument cluster. For further diagnosis
of the tachometer or the instrument cluster circuitry
that controls the gauge, (Refer to 8 -
ELECTRICAL/INSTRUMENT CLUSTER - DIAGNOSIS
AND TESTING). For proper diagnosis of the
crankshaft position sensor, the engine speed sensor,
the PCM, the ECM, the PCI data bus, or the electronic
message inputs to the instrument cluster that
control the tachometer, a DRBIIIt scan tool is
required. Refer to the appropriate diagnostic information.

wiram · Apr 1, 2014

When I plug my programmer in it reads the rpm's where they should be. It works in the upper Rpm range and once you get to a cruising speed or a dead stop it drops down by 1000 rpm's. The programmer reads where they actually are.

Redtruck-VA · Apr 1, 2014

wiram said:
When I plug my programmer in it reads the rpm's where they should be. It works in the upper Rpm range and once you get to a cruising speed or a dead stop it drops down by 1000 rpm's. The programmer reads where they actually are.

Does the initial startup complete a good Actuator Test?

wiram · Apr 1, 2014

Not sure what your asking exactly. Is this in the trucks owners manual

Redtruck-VA · Apr 1, 2014

wiram said:
Not sure what your asking exactly. Is this in the trucks owners manual

This happens every time you turn on the ignition.

Actuator Test - Each time the cluster is put
through the actuator test, the tachometer needle will
be swept to several calibration points on the gauge
scale in a prescribed sequence in order to confirm the
functionality of the gauge and the cluster control circuitry.

wiram · Apr 1, 2014

I just did it and it ran through everything but it still doesn't read right

MegaMouseGW · Apr 1, 2014

Sounds like his cluster is going bad.

wiram · Apr 1, 2014

That's part of my tach. In the dash right?

Redtruck-VA · Apr 1, 2014

I would check the crank sensor/plug/wiring. Maybe replace the sensor. If still no good, then I'd talk to the dealer to see if any PCM software upgrades are available that addresses this specific problem. If still no good then I'd probably have it scanned at the dealer to determine the specifics of this problem. If the cluster is self checking properly then I'd focus more on signal input. Good luck and let us know what you find...

wiram · Apr 1, 2014

I'm taking it in hopefully Friday for headers, cat delete, Y-Pipe, and 180 t-stat. Here gonna run diagnostics on it. It has a rough idle he thinks it could be a vacuum leak. Could that have anything to do with the tach. But I'll talk to him about the crank sensor and tach. Issue to see what he thinks. Thanks for the help and I will post my findings on here.

WulfGang · Apr 1, 2014

He may be having the same problem I'm having that has been addressed in another thread where it seems the culprit is the "lead free solder" used on the contact points on 2 chips.

Lead free solder develops hair line cracks and loses it's conductivity.

I watched a guy on Youtube "reflow" his contact points and fixed his problem.

I actually had to do "reflows" on my old "FAT" Ps3 and a big screen TV.

The TV is still going good. The PS3 well... the third time I had to bury it.

I hooked my Diablo up for the first time today.
I'm enjoying the ability now to see my RPM's lol.

I had NO idea I was doing 1900 rpm @ 70mph.

I even created a thread asking about hooking up aftermarket tachs - which, I'm still going to do because, I'm not satisfied with what the Diablo has for "tachs".

*ETA*
Let me clarify, the "2 chips", are chips on the back side of the tach IN your cluster.

You have to remove the entire cluster (after taking apart the dash area) to fix this.

Here is the YT link:
https://www.youtube.com/watch?v=ufQ1t4eOwkM

You can also type in "Fix for DODGE RAM tach" into the YT search field.

wiram · Apr 1, 2014

I'll check into that. Good info. Thanks

Redtruck-VA · Apr 1, 2014

WulfGang said:
He may be having the same problem I'm having that has been addressed in another thread where it seems the culprit is the "lead free solder" used on the contact points on 2 chips.

Lead free solder develops hair line cracks and loses it's conductivity.

I watched a guy on Youtube "reflow" his contact points and fixed his problem.

I actually had to do "reflows" on my old "FAT" Ps3 and a big screen TV.

The TV is still going good. The PS3 well... the third time I had to bury it.

I hooked my Diablo up for the first time today.
I'm enjoying the ability now to see my RPM's lol.

I had NO idea I was doing 1900 rpm @ 70mph.

I even created a thread asking about hooking up aftermarket tachs - which, I'm still going to do because, I'm not satisfied with what the Diablo has for "tachs".

*ETA*
Let me clarify, the "2 chips", are chips on the back side of the tach IN your cluster.

You have to remove the entire cluster (after taking apart the dash area) to fix this.

Here is the YT link:
https://www.youtube.com/watch?v=ufQ1t4eOwkM

You can also type in "Fix for DODGE RAM tach" into the YT search field.

Not sure where your new thread on Tach's is located. But using a Shift Lite that includes a rpm readout is a solution.

WulfGang · Apr 1, 2014

I LOVE the look/size of the stock tach in the cluster. If only it'd work...

I do plan on reflowing it. When I get more spare time and warmer weather! haha

wiram · Apr 1, 2014

I've had this issue for over a year now and it bugs me all the time and I'm pushing to have everything running 100% this year.

WulfGang · Apr 2, 2014

I'd like to think if I can disassemble the chip board of a big screen tv and reflow the 12odd contact points for the voltage regulation on the tv...

If I can completely disassemble a PS3 "FAT" and use a heat gun to "reflow" the solder balls that go between the chip and the motherboard and put it back together - with no "extra pieces" - I'd like to think I could do this project as well.

I think the video is pretty thorough.

It looks like you get snow where you're at as well. This isn't something I'd want to even think about doing till it warms up.

Also, the thing about lead free solder is that it is gonna be prone to doing this stuff all over again.

I can't believe my TV is still going.
The PS3 lasted about 3 months before I had to reflow it the second time.
After the second time it lasted about 3 months again.

IMO, being this is a pretty common thing on these trucks it seems DODGE! should be the ones on the hook for fixing it.

wiram · Apr 2, 2014

Is that part of the tach. In the dash? Could I install an aftermarket one? I don't really know anything about this subject.

wiram · Apr 2, 2014

I talked to the guy at the shop and he figured it was the throttle position sensor.

Redtruck-VA · Apr 2, 2014

wiram said:
I talked to the guy at the shop and he figured it was the throttle position sensor.

IMO, find another shop...

Rpm gauge

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