Tachometer needle intermittent not working properly?

Hello,

The problem is either going to be with the Power-train Control Module, the instrument cluster itself, or the CAN system connecting the two together. In the diagrams down below I have included the diagnostic troubleshooting guide from the vehicle manufacturer for an intermittent tachometer. Please go through this guides and get back to us with what you find out.

Thanks,
Alex
2CarPros

Recently had a new crankshaft pulley installed by garage, now the rev counter doesn't work and the plug heater lamp is flashing. Any ideas ?

Hey DAVID CONROY,

You have the 2.5L turbo diesel motor?

Were these faults present straight away after the replacement of the crankshaft pulley?

I do not have the details for that motor but the pickup for the crankshaft position sensor may be part of the pulley.

I would say returning to the garage to get them to recheck the fitting would be the first thing to do. I would be wary that if the bolt that holds the pulley has come loose and the pulley is starting to work its way off that driving it further could end up causing you some fairly serious engine damage.

Regards, Joe

How do I get to the light bulbs behind the tach to replace them when one has burned out? How do you get the clear plastic cover off that's in the dash to get to the light bulbs?

disable SRS system then remove the screws and pull the center instrument panel finish panel out from the instrument panel. disconnect the electrical connectors and remove the radio and center instrument panel finish panel. remove the screws and remove hood latch release handle. remove the instrument panel steering column cover. remove instrument panel steering column opening cover reinforcement. position column gear shift lever aside, if equipped. pull instrument cluster finish panel out from the instrument panel. disconnect the connectors and remove the cluster finish panel. remove the instrument cluster screws and disconnect and remove cluster. Twist and remove bulb needing replaced then reverse procedures to install.

I own a 1995 Ford Ranger and recently replaced the old instrument cluster (no tach) with a fully functional cluster from a 2001 Ford Sport Trac (with tach).

The cluster is completely compatible and has no issues, except for the fact that the tach acts sluggish and weak.

I would like to know what all is involved in the tachometer receiving its signal and how can I troubleshoot the issue? Its worth mentioning that before replacing the original instrument cluster, I did have a check engine light, and the speedometer did not function. After replacing the VSS the check engine light went off but the speedometer did not function. I assumed the cluster was bad, but could the speedo cable be bad as well? Does this electric cable have any effect on the tachometer?

hello and thanks for donating


a slow and sluggish tachometer is normally due to faulty grounding of the tach. since the original cluster didn't have a tach, there is no ground being presented at the cluster for a tach..an easy way to check is just get a loose piece of wire and ground it good to a bolt or something in the cab of truck, then wire it to the tach. if it works fine then you need to run a good permanent ground.

the speedo cable does not affect tachs, the tach is electronic while the speedo is manually driven by cable.

I'm going to try the ground wire. You wouldnt happen to know which wire in which connector it is? Or have a wiring diagram you could share?

My speedometer uses the VSS sensor connected to the wiring harness. What exactly does the Tach use to receive its signal? Thanks.

The tach circuit terminal connector ground pin is pictured below.. The tach uses the ignition coil to get its signal..

Is there anyway you can send the complete blown up image to my email? Its too small to make heads or tails of on this forum.

[email protected]

yes, email sent, sorry about that.

Awesome! Thank you sir!

2.3L dual coil non-distributor EEC IV set-up.

Tach acting erratic, idle rough only at op temp and finally threw a check engine light with code 222 and 224. Sometimes tach shows no rpm at all while idling.

Have replaced plugs (gapped at 0.43), plug wires, coolant temp sensor, coil packs and all wire connections/connectors visually seem in very good shape and condition. Now only code 222 shows. KOEO passes with a 111 now, but KOER shows a 998 fault and then 222. Tach still erratic and idle no better than before. Runs smooth above idle, starts fine with engine hot or cold.

What's left in my thoughts as the cause:
22k ohm wire bad, if equipped. Condenser/capacitor on one of coil pack mount bolts bad. ICM, PCM or CKP (those three each are expensive to replace as a guess). How can I narrow what's wrong to the actual failed component without replacing all what I believe left to try?

Any other thoughts, diagnosis and self-tests with procedures will be greatly appreciated.

John

With a song and a prayer, pulled the trigger on a ICM unit. That was it. No codes anymore and tach working fine. No check engine light, passed KOEO and passed KOER test. Cheers

Good to hear, please use 2CarPros anytime we are here to help.

1994 Ford Ranger 4cyl dual distributor Actual RPM is twice what is being displayed on Tachometer.... & Check Engine Light is on...

Dual distributor? No such thing.

I assume you have the 8 plug, 2.3 engine.
The first thing you need to do is to determine if both sides of the ignition system are actually working. Test for spark at all 8 spark plugs. It's entirely possible for one side of the ignition module to be burnt out or failing for some external reason.

I replaced the ICM recently,the engine is running great,except for a 412 code (can't control rpm) and my tachometer is not working either.I checked for voltage from pin 12 (IDM tan/yellow wire)) on ICM all the way to PCM including tachometer.test connector and I'm getting 0 volts in that wire.Could it be lack of ground or short or open circuit,or all of the above?
Thanks for your help and Happy Holidays .

Hi,

It could be any of the above issues.

Lets start with this. I have a flow chart for testing. I will give you the start of it. Once you do this and let me know the results, I can move you to the relevant next steps.

________________________________

1994 Ford Truck Ranger 2WD L4-140 2.3L SOHC
KE1 - Check For RPM Drop
Vehicle Powertrain Management Computers and Control Systems Testing and Inspection Pinpoint Tests With EEC IV (OBD I-A System) Pinpoint Tests KE - Idle Air Control Control Solenoid KE1 - Check For RPM Drop
KE1 - CHECK FOR RPM DROP
Diagnostic Trouble Code (DTC) 412 indicates that during Engine Running Self-Test, engine rpm could not be controlled within the Self-Test upper limit band.

Possible causes:

- Open or shorted circuit.

- Throttle linkage binding.

- Improper idle airflow set.

- Idle Air Control (IAC) solenoid contamination.

- Items external to Idle Air Control system that could affect engine rpm.

- Damaged IAC solenoid.

- Damaged Powertrain Control Module (PCM).

- Key "OFF".

- Connect engine tachometer.

- Start engine.

- Disconnect IAC harness connector.

- Does rpm drop or stall?

Yes -- Go to KE2. See: Computers and Control Systems > Pinpoint Tests > KE2 - Check For Other DTCs

No -- Go to KE3. See: Computers and Control Systems > Pinpoint Tests > KE3 - Check For Other DTCs

__________________________________________________

Also, here is the test for the tach not working

1994 Ford Truck Ranger 2WD L4-140 2.3L SOHC
R: Tachometer Always Indicates Too High or Too Low, No Tach Indication/Tach Indication Erratic
Vehicle Instrument Panel, Gauges and Warning Indicators Instrument Cluster / Carrier Testing and Inspection Pinpoint Tests Electronic Instrument Cluster R: Tachometer Always Indicates Too High or Too Low, No Tach Indication/Tach Indication Erratic
R: TACHOMETER ALWAYS INDICATES TOO HIGH OR TOO LOW, NO TACH INDICATION/TACH INDICATION ERRATIC
R1 CHECK WIRING


^ Make sure engine is not misfiring.


^ Disconnect battery ground cable


^ Remove instrument cluster.


^ Using Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent, measure resistance between connector B Pin 20 and coil.


^ Wiggle connections and wiring near coil to check for intermittent connection.


^ Is the resistance less than 100 ohms?


Yes


REPLACE instrument cluster. RECHECK operation.

No

SERVICE wiring Circuit 11 for open circuit.

_________________________________________

Let me know what you find,

Joe

Hi Joe, thanks for the fast response,appreciate it. First of all (sorry I forgot to mention this) this is an aftermarket tachometer. I can't check for RPM drop because the wire that carries the signal from ICM (pin 12,tan/yellow wire) to PCM and eventually to tachometer, is dead, 0 volts or pulses. I'm hoping I'm not having a short in that circuit and fried that part of the brand new ICM which could be a possibility,couldn't it?
Again, thanks for your fast response and help.

Hi,

If you aren't getting power, it is very possible. However, what was done that made you think it could have fried?

Hi, nothing to the best of my knowledge.I followed procedures; disconnected the battery,unplug ICM,clean the area thoroughly,and I mean thoroughly. applied some dielectric grease to ICM, put it back on plugged it in and reconnected battery.
Again, thanks for your fast response and help.

Was the ICM an aftermarket part? Also, is the vehicle still running? If it isn't let me know.

Yes,the new ICM is from Std.Motor Products.Yes ,she's running,little rough idle ,though.Actually,I ran the koer test again and I got a 332(EGR low flow)and a 411(cant control rpm)codes.Funny thing,I took some voltage reading with the voltmeter from the tachometer service connector and got between 10 and 12 V.,but no pulses showed on test light,though.
Thanks again.

The EGR code can be the result of carbon. However, and I hate to say this, but I think you got a bad part (ICM).

I figured as much.This is a new ICM, so there must be a short somewhere in that specific circuit. the one that carries the signal from pin 12 on ICM to #4 on PCM.I guess it's "find that freaking short"time.
Thanks a lot,buddy, appreciate the inputs.

Your very welcome. I honestly don't know what else it could be. And like you, I wouldn't want to seek out that short. LOL

Since the ICM is new, is it under warranty?

Hey,buddy,welcome to the "ran out of options"club. One more thing to do,get me a bottle of Tylenol's,(for the headaches I am sure l'll have trying to "nip this thing in the bud") before replacing the ICM again. Maybe the manufacturer can help me out.
Thanks for your concern,I'll keep you posted.

Tylenol, the final remedy. LOL I've been there. As far as the manufacturer, I would hope they back you. If they don't, it says a lot about them.

Joe