Hey everyone hows it goin? My name is Pete and i figured it was about time i chimed in over here.
With that being said i do have a problem that i could use a little help with. I have an 02 1500 3.7 2wd and i just recently had a couple fault codes pop up. i have P1491, which i know through my searches that its the condenser fan relay fuse, and the more infamous P1687 code which is, from what ive gathered, the "no bus" gauge failure code or something along those lines.
here is were my problem begins however, from everything ive seen so far, when you get the P1687 code, you have some sort of instrumentation failure, BUT, i have this code and all my gauges are working fine...
so im a little stumped on why i am getting this code.
if you have any recommendations, questions, comments, anything let me know and have a good day yall!

 

This is where I would begin. It's easy and best of all.... free. This should work for your year.


SELF TEST
The instrument cluster self test will put the instrument cluster into its self-diagnostic mode. In this mode the instrument cluster can perform a self-diagnostic test that will confirm that the instrument cluster circuitry, the gauges, and the indicators are capable of operating as designed. During the self test the instrument cluster circuitry will position each of the gauge needles at various calibration points, illuminate all of the segments or portions in the Liquid Crystal Display (LCD) unit, and turn all of the indicators ON and OFF again.

Successful completion of the self test will confirm that the instrument cluster is operational. However, there may still be a problem with the CAN data bus, the Powertrain Control Module (PCM), the Totally Integrated Power Module (TIPM), the Transmission Control Module (TCM), the Occupant Restraint Controller (ORC), the Controller Anti-lock Brake (CAB), the Wireless Ignition Node (WIN) or the hardwired inputs to one of these electronic control modules. Use a diagnostic scan tool to diagnose these components. Refer to the appropriate diagnostic information.

1. Begin the test with the ignition switch in the OFF position.
2. Depress the odometer/trip odometer switch button.
3. While still holding the odometer/trip odometer switch button depressed, turn the ignition switch to the ON position, but do not start the engine.
4. Release the odometer/trip odometer switch button.
5. The instrument cluster will simultaneously begin to illuminate all of the operational segments in the LCD unit and perform a bulb check of each operational Light Emitting Diode (LED) indicator. The LCD segments and LED indicators remain illuminated as each gauge needle is swept to several calibration points and back. If a VFD segment or an LED indicator fails to illuminate, or if a gauge needle fails to sweep through the calibration points and back during this test, the instrument cluster must be replaced.
6. The self test is now completed. The instrument cluster will automatically exit the self-diagnostic mode and return to normal operation at the completion of the test. The self test will be aborted if the ignition switch is turned to the OFF position, or if a vehicle speed message indicating that the vehicle is moving is received from the PCM over the CAN data bus during the test.

 

Thanks dirtydog, i will go give this a try and will report my results soon. Definitely like the free part too!

 

I wanted to say thank you, however i still have not gotten around to doing this because i am dealing with a much more serious problem. The other day when getting out of work my truck decided she was going to throw a tantrum. She drove fine all day but when i got out and started her up, she was ok for a second, then she shook like crazy and stalled out.
now i can not get her to start unless i press the gas down while turning the ignition, and when i finally am able to, she wont stay running unless i have my foot on the gas. Idle is a no go basically.
I checked my ignition coils and they are all good and getting spark, just swapped out my plugs as well.
I got some more codes that just popped up and i have no idea where to start
anyways here they are, you guys are my life line at the moment:

p0113 Intake Air Temperature (IAT) Sensor Circuit High Voltage
p0340 Camshaft Position (CMP) Sensor Circuit
p0352 Coil is not reaching peak current at the right time (last digit is coil number p0505 Idle Control System Malfunction
p1491 Rad Fan Control Relay Circuit

 

Is your main truck battery ok?
Reason i ask is, with all the electronics on these trucks you must have a good battery.
If a cell is breaking down causing slightly low volts, these trucks act up terribly.
Do a swap with a loan battery and see if the problems go away.
Its a quick thing to do and i have seen issues go away immediately this was done.
Worth a shot.
Al.

 

My battery is all good. So where should i go from there?

 

Replace the cam angle sensor with a new one. That is likely exactly where the problem is coming from.

If you still have the IAT code then try cleaning the throttle body, with Throttle Body cleaner. If code persists (after a reset by disconnecting the battery) then replace the IAT sensor with a new one.

The Radiator Fan circuit relay should be located in the fuse box under the hood, remove it and check for corrosion, if there is corrosion clean it off with a brass wire brush, add some dielectric grease, reset truck again (by disconnecting + battery terminal for 60 secs) and start her up again. If that code persists then replace the relay. if the code is still there after a new relay then you might have some corrosion on the underside of the fuse box which is causing electrical problems. Search on here for fuse box corrosion and you should be able to find a how-to.

as for the Coil code, I think that might be related to the Cam position sensor... if that doesn't go away, check all your coil connections (as you said you swapped some of them)

We'll go on from there once you update us on which ones went away or not.

 

So here's where i am:
Replaced the cam position sensor, started up, no change.
Pulled the battery and the fuses for the PCM, let her sit for a while, plugged back in and started again. Runs the same terrible way and is blowing white smoke out the tail pipe and is not flashing anymore codes up. Also, the check engine light is now off.

 

Time for a compression and leak down test... kinda sounds like you might have a busted head gasket....

 

I would think that i would still be able to start and run my engine normally then. might be a little rough but i would actually have an idle and not have to keep the throttle all the way open to start.