2004 ranger xl 2.3 automatic
Somewhere around 300k miles
Original engine blew at 260k miles and I replaced it with a 2.3 out of a 2006 Mazda B2300 with 63k miles but I used the harness of of the 2004 engine because the 2006 harness was different. Everything worked perfectly to begin with but after about 20k miles the gauge cluster started to work intermittently. The ground cable was corroded so I cleaned it and used the protective spray and the issue went away for a year or so. Now it’s acting up again but the cables are clean and I’m not sure what else to look for.

Occasionally the speedometer and tachometer will bounce around or go completely to the right. Sometimes the fuel and temperature gauges work and sometimes it’s a mix of everything listed above.

From what I’ve read it could be the pcm/ecm or the gauge cluster itself. I have tried the self diagnostic process when everything is working but the diagnostics don’t seem to work. Is there a way to test the pcm/ecm or gauge cluster?

 

2004 Ranger was 1st year for the Digital Cluster(HEC) and Smart Junction Box(SJB, body computer)
Yes, the self diagnostics often don't work on these HEC

Oil pressure, Temp and Fuel gauges were still analog, i.e. they use senders/switches connected directly to Cluster
Tach and speed signals are digital
But all share same 12volt and grounds in the cluster

Cluster wiring diagram below

You can't just swap clusters after 2003, because the HECs have a micro-processor they are "married" to the PCM, they do a "handshake" with key on, if they don't recognizes each other then No Start, this was to prevent people swapping in lower mile odometers
HEC also has PATS built-in, so you need to reprogram you current Keys into new HEC, along with "re-marrying" it to PCM

Since you did find a wiring issue last year I would pursue that direction, on the ground and 12v wiring, using the diagram

And since you didn't mention any running problems with the engine I wouldn't think PCM is the issue

 

So if engine is running fine, which it is there would be no reason to suspect the pcm?

 

No, not that I would suspect, especially if Tach drops out but not actual engine RPMs

Do you have cruise control?
If so, does it stop working when speedometer drops out?
PCM does generate the speed signal(2001 and up) and sends it out to Cluster and cruise, both

Also since you have an automatic, the shifting would be erratic if there was a internal PCM speed signal issue

 

Engine runs great at all times, even when gauges are acting up. No cruise control.

As far as transmission and shifting goes it does have a glitch that I believe is caused by the valve body but it could be the torque converter itself. It will shift fine as long as you stay 45mph or less. If you get over 45mph for any length of time it will flash the “od” light in the dash and shifts hard. As soon as you turn the truck off and restart it the od light stays off until you get back above 45mph for any length of time. 99% of the driving I do is on back roads and I never get over 40mph so I rarely see the blinking od light and the transmission shifts flawlessly. I would say there is no erratic shifting at all.

Now that I’m thinking about it, even when the gauge cluster is acting up or out completely the od light will still blink if you get over 45mph.

 

OD Light flashing means there will be transmission codes set in memory
P0700 to P0804, most OBD2 readers can't "see" these, check model number of reader it will say directly it CAN READ transmission codes, no mention means it can not

OBD2 list seen here: https://www.therangerstation.com/tec...trouble_codes/