Jumpy / Erratic Speedometer
Thread Starter
Junior Member
Joined: Dec 2015
Posts: 7
Likes: 0
Here's an update:
Got the Dongle and Torque app, the speed jumps on that as well. So I replaced both speed sensors (one at a time) and the problem persists.
So my question is, because the Torque app is showing the same jumps is it likely to be in the wiring between the sensors and the cluster?
Things to note: when the torque app is reading the little green indicator on the screen in the torque app speedo dims and pulses... is this normal? or is it indicating a erratic signal? I can still drive the car: when the truck is standing still (like at a light) the speedo jumps and can stall the truck, but once I get going the speedo levels out and is fine.
Last question... is this worth fixing? Is a speedo swap worth it? The truck runs good, 125K miles, and lots of new parts to keep it afloat, but is rusted and will need a new muffler in the spring.
Got the Dongle and Torque app, the speed jumps on that as well. So I replaced both speed sensors (one at a time) and the problem persists.
So my question is, because the Torque app is showing the same jumps is it likely to be in the wiring between the sensors and the cluster?
Things to note: when the torque app is reading the little green indicator on the screen in the torque app speedo dims and pulses... is this normal? or is it indicating a erratic signal? I can still drive the car: when the truck is standing still (like at a light) the speedo jumps and can stall the truck, but once I get going the speedo levels out and is fine.
Last question... is this worth fixing? Is a speedo swap worth it? The truck runs good, 125K miles, and lots of new parts to keep it afloat, but is rusted and will need a new muffler in the spring.
Here's an update:
Got the Dongle and Torque app, the speed jumps on that as well. So I replaced both speed sensors (one at a time) and the problem persists.
So my question is, because the Torque app is showing the same jumps is it likely to be in the wiring between the sensors and the cluster?
Things to note: when the torque app is reading the little green indicator on the screen in the torque app speedo dims and pulses... is this normal? or is it indicating a erratic signal? I can still drive the car: when the truck is standing still (like at a light) the speedo jumps and can stall the truck, but once I get going the speedo levels out and is fine.
Last question... is this worth fixing? Is a speedo swap worth it? The truck runs good, 125K miles, and lots of new parts to keep it afloat, but is rusted and will need a new muffler in the spring.
Got the Dongle and Torque app, the speed jumps on that as well. So I replaced both speed sensors (one at a time) and the problem persists.
So my question is, because the Torque app is showing the same jumps is it likely to be in the wiring between the sensors and the cluster?
Things to note: when the torque app is reading the little green indicator on the screen in the torque app speedo dims and pulses... is this normal? or is it indicating a erratic signal? I can still drive the car: when the truck is standing still (like at a light) the speedo jumps and can stall the truck, but once I get going the speedo levels out and is fine.
Last question... is this worth fixing? Is a speedo swap worth it? The truck runs good, 125K miles, and lots of new parts to keep it afloat, but is rusted and will need a new muffler in the spring.
4.6, The True Triton
Joined: Nov 2011
Posts: 337
Likes: 14
From: Michigan
Member
Joined: Dec 2015
Posts: 37
Likes: 3
From: Portland, OR
The Torque apps reports what the PCM is saying that it is seeing, not what's actually on the sensor wire. Since an instrument cluster issue is unlikely to cause the engine to stall, then the stalling problem is between the sensor and the PCM.
The green indicator flashing/dimming is simply Torque telling you when it actually got an update of the value from the PCM, nothing more. The more PIDs you collect, the longer between updates.
Since the erraticness is happening in park, and affects the engine, then the issue probably has nothing to do with the speedometer senor and more to do with the crank position sensor or something. Since it comes and goes, I'd suspect a grounding problem before I suspected a loom issue. So, my first thing might be to check PCM grounds -- heck, PITA though it is, I'd probably get the dielectric grease and just go clean and grease all the computer grounds. IIRC from my rust belt days, cold weather and road salt bring out all sorts of fun grounding issues.
The green indicator flashing/dimming is simply Torque telling you when it actually got an update of the value from the PCM, nothing more. The more PIDs you collect, the longer between updates.
Since the erraticness is happening in park, and affects the engine, then the issue probably has nothing to do with the speedometer senor and more to do with the crank position sensor or something. Since it comes and goes, I'd suspect a grounding problem before I suspected a loom issue. So, my first thing might be to check PCM grounds -- heck, PITA though it is, I'd probably get the dielectric grease and just go clean and grease all the computer grounds. IIRC from my rust belt days, cold weather and road salt bring out all sorts of fun grounding issues.
Thread Starter
Junior Member
Joined: Dec 2015
Posts: 7
Likes: 0
So the problem is fixed!
After poking around a bit for loose grounds and such i followed the the wiring harness that carries the wires from the trans sensors. It runs up to the engine compartment around the right side of the motor to a large cluster connector. That harness is supposed to be held to the firewall by a push clip. That clip came loose and the harness fell down next to the head. The wires got hot enough to soften the wire insulation to where they stuck together, but not enough to destroy them, so I pulled them apart, wrapped them with electrical tape and zip-tied the harness up and away from the engine. There was a spark plug wire that was touching them too so I zip-tied that one up and away. So my guess is that the interference was either coming from the wires being stuck together or it was picking up interference from the plug wire.
Thanks to everyone for your help!
After poking around a bit for loose grounds and such i followed the the wiring harness that carries the wires from the trans sensors. It runs up to the engine compartment around the right side of the motor to a large cluster connector. That harness is supposed to be held to the firewall by a push clip. That clip came loose and the harness fell down next to the head. The wires got hot enough to soften the wire insulation to where they stuck together, but not enough to destroy them, so I pulled them apart, wrapped them with electrical tape and zip-tied the harness up and away from the engine. There was a spark plug wire that was touching them too so I zip-tied that one up and away. So my guess is that the interference was either coming from the wires being stuck together or it was picking up interference from the plug wire.
Thanks to everyone for your help!