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Discussion Starter · #1 ·
I have a 1997 Dodge Ram 2500 12 valve manual. The speedo and tacho are pegged constantly and all of the other gauges have no reading constantly. The previous owner tried to replace the cluster, and it didn't change anything. How do I fix this?
 

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1997 4X4 2500 automatic 240,000 regular cab
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I have a 1997 Dodge Ram 2500 12 valve manual. The speedo and tacho are pegged constantly and all of the other gauges have no reading constantly. The previous owner tried to replace the cluster, and it didn't change anything. How do I fix this?
There are just two hot wires going to the cluster and three grounds supplying it. The grounds do all or most of the switching. You can locate those two hots by color once you look up the pin out page on the connectors in the FSM. I took my cluster partly out and unplugged the two connectors, located the two hots, tested them. You can also trace the copper from those hots and locate gauges, see if a gauge’s two wires are working. Each gauge terminal has a screw head you can test. There are fuses for those two hot wires, check the # 3 in the box in the cab. But there is another one too. That’s all I can remember but your FSM will show the various wires to check. This is where having a paper copy helps.
 

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Discussion Starter · #3 ·
So check all of the wires and the fuses for the wires. Do you think the cluster computer could be fried? I also heard stuff about the ess. Also, the odometer doesn't work and flashes constantly. I'm new to the Cummins world. I practically rebuilt my old 95 Ford 7.3 from the ground up and was very familar with how it worked. Cummins is different, but I am not disappointed.
 

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The Computer (pcm) controls certain gauges in the cluster, like tach, generator light. It wouldn’t cause the entire cluster to go out. The ESS for instance sends its signal to the PCM which then sends its signal to the cluster. Sounds like you have a bad fuse or ground. Check fuse 12 in the fuse block under the dash, see if it’s hot on both ends when you turn on the accessories with the key. Fuse 12 powers the voltmeter, tach, and speedo and other stuff. Warning lights get grounded on and off by various sensors. Does anything at all work on your cluster?
 

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Discussion Starter · #5 · (Edited)
Most of the lights turn on, but I don't know if they actually work. The wait to start light doesn't work. None of gauges work. The tach and speedo are pegged at max and the other ones show 0 constantly. The odometer doesn't keep track of mileage and flashes at a constant pace.
 

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Did you check fuse 12? Tach and speedo both get signal from the pcm, but the pcm needs a good ground, I think it uses the one that’s on top of the front if the head, easy to check, clean. So the Gen. light is off too? The gen, speedo and tack all get their 12V from #12 fuse, gotta check that
 

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Did your previous gauges all behave this same way? I’m wondering if you replaced a good one that had a system problem with one that got damaged at the wrecking yard. Which is what I did, got one from a wrecker that had a circuit broken, between the warning lights below the fuel gauge and the tach and speedo. Down where those copper lines get close to the edge, mine busted. If it shorted it might peg the two next gauges that circuit goes to which is the tach, then speedo, then voltmeter. The book shows VM first but it’s last
 

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i discovered my problem by disconnecting the two connectors on the cluster and finding and testing the hot wires in them. When I determined they were hot (one from fuse 12 is orange) with key on, I traced the hot wire on the circuit board until I found where it was broken. I stared at the copper lines for a while to trace them. From fuse 12 to oil pressure first I think, then fuel level, then tach, then three warning lights on bottom, something like that. It’s all visible and traceable. Then I added a wire to jump over the break. You can download the FSM by going to the first menu of this website, it’s got a great section on the cluster, page 8E 21. Don’t look at the gas engine one
 

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What do you mean by "the odometer flashes at a constant pace"? To my knowledge they didn't make a digital display for the odometer in 97...
 
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Discussion Starter · #12 ·
My Cummins was built in December of 97 so it's basically considered a 98. My bad. Also, you think my problem is most likely the wiring behind the cluster? Why would the tach and speedo be pegged constantly? Key off and on. Also, the other guages are receiving power. They rise from the very lowest position to 0 when the key turns on. Also, the heater grid and cruise control also doesn't work.
 

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Discussion Starter · #13 ·
I did the cluster check with the odometer pin. It showed codes 920, 921, and 999. Then it did the needle sweep and the tach and speedo went back to 0 instead of being pegged at max.
 

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My Cummins was built in December of 97 so it's basically considered a 98.
Is it a 98? The 98's instrument cluster is entirely computer-controlled and diagnosing will be wildly different. Does your dash look like picture #1:
dodgeraminstrumea.jpeg


Or picture #2:
hqdefault.jpg
 

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Discussion Starter · #15 · (Edited)
Mine looks like the first picture with the double DIN radio. Mine is also a manual. All the fuses are good, and I unplugged the ESS and the Check Engine light popped up. I can't connect to the PCM through the OBDII. I will be driving and some of the lights turn on like ABS, parking brake, and low fuel the they will go away. I also don't get a Wait to Start light. I don't think the heating grid works. I did the cluster check with the odometer pin and codes 920, 921, and 999 popped up. It did the needle sweep. But everything stays at zero. It gets power because the needles raise from the lowest point to 0 when you turn the key on. I was going to see if anyone could plug into the OBDII and do a reflash. Is this the right way to go?
 

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OK, you've got a 98 then. You may have some better luck in the 98-02 forums as most of here have the 94-97's with a more 'analog' cluster. In the 98, the PCM talks to the cluster via a data bus and tells it speed, rpms, temp, oil pressure, etc, and the electronics in the cluster drive the needles and lights accordingly.

Is is the low fuel lamp, or is it possibly the low washer fluid lamp? The reason I ask is that the parking brake lamp and the low washer fluid lamp are hardwired -- they are not controlled by any kind of electronics (well, the electronics can turn on the brake lamp, but it's also turned on by a dumb switch on the parking brake). Might be a clue, anyway, that the parking brake light especially is intermittent.

920 and 921 indicate that the cluster is not receiving vehicle or engine speed data from the PCM. You may have a fried PCM, but at least it's 'awake' enough to throw the CEL signal to the cluster, so that's kind of interesting. Would also explain not seeing anything on the OBD-II port. Do you get any or all of the bulb checks (especially WTS would be interesting) when you key-on?

Does your cruise control work?
 

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Discussion Starter · #17 ·
Wait to start light does not come on and cruise control does not work. The low fuel light comes on since the guage shows no fuel. The parking brake light comes on when it wants to or when I have the parking brake on. It seems like the longer the key is on, the more lights turn on. I first start it everything is off, then after a while the lights will come on.
 

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I think almost certainly you have a dead pcm, but that doesn't necessarily mean 'fried', it could just mean no power or ground to it. The WTS light is controlled directly by the PCM (not by the cluster), so no bulb check there is a sign that it's not coming up. You said you checked all the fuses so if it's not a fried PCM, it's probably a loose/missing ground somewhere. I'm unsure where the PCM grounds on the 98 12V's. It may be on the front of the cylinder head? At the very least there should be a ground there. Check all the engine<->chassis engine<->battery grounds too.
 

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Discussion Starter · #19 ·
I did take off and cleaned the ground liberally on the head. I guess I'll just have to crawl around it and find and clean all the grounds.
 

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Discussion Starter · #20 ·
I was driving it today, and it boiled the driver side battery. I was also talking to the previous owner and he said that everything stopped working all at once. Cruise, WTS, and the cluster all went dead all at once.
 
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