Cat 320d excavator speed sensor(s)

[bsamot69]

2008 CAT 320d excavator, 6.4 Acert engine, serial phx01833. CAT is vague on location of engine speed sensor. I have a sensor front right side near injection pump and a sensor on right rear near flywheel.
To remove the front sensor is going to be a challenge. It's under behind all manner of brackets tubes etc. does anybody have experience removing and installing this sensor? So far my wobbly long extension does not reach the bolt. How in the world is this done by the CAT pros?
The rear sensor is reachable.
I did some tests on the circuits which revealed the front is receiving 8v ref with key on sensor disconnected. The rear sensor has no voltage with key on. I want to check ecm inputs outputs but finding a pin out of the connector is elusive. I need help with:
A way to get the front sensor out
An ecm connector pinout diagram
And your prayers and guidance
Thank you in advance

 

[Gary Layton]

Good description of your problems...I bet these guys can help.

 

[Nige]

Location of engine speed sensor is shown as Ref #6 on the attachment.
There is also a camshaft speed sensor Ref #1 (same 238-0120 Part # as above) mounted on the fuel injection pump.

Check your message inbox for an electrical schematic.

What problem do you have exactly.? Any Active Diagnostic Codes.?

 

[bsamot69]

The machine codes 39 190-8 and 39 586-5 are 2 codes. I misplaced my notes. These 2 codes I remember. The machine starts and runs. The dial to increase rpm is non operational. The machine is in limp mode so can only move it around at idle. The boom and bucket controls are all functional.
I checked the connection at both speed sensors. The sensor mounted by injection pump has 8volt supply. The sensor connector in back by flywheel has no voltage. Looking at the schematic both sensors receive voltage from same source. #10 at ecm connector. I hope I'm reading the diagram correctly. Am I looking for a break in harness?
I checked the resistance of the rear speed sensor. It measured .3 ohms. When it stops raining I'll go check why there is no sensor voltage at connector. I can recheck the active codes also. I appreciate the information you sent me. Any other suggestions?

 

[Nige]

From the electrical schematic the supply to both speed/timing sensors should be 8v. My suspicion would fall on the short section of wiring harness between the splice and the primary sensor (or maybe even the splice itself) seeing as the secondary sensor has power. When I say "short" that's how it is shown on the schematic. In practice it may be longer than the pigtail it appears to be.

Just a thought but have you tried measuring the supply voltage to the primary sensor on the flywheel housing with the 2-pin connector unplugged.? It shouldn't make any difference but best to check.



Also attached troubleshooting procedures for the two Codes.

 

[bsamot69]

Checked all the connections and found the connector had not snapped together. Yeah! The dial switch code came up. Per the diagnostic sheet you sent me, I performed the tests . The switch is good , however, the harness wires have no continuity. Seems I'll be looking for damaged harness.
I discovered two switches on back off armrest that control the engine speed manually. Those work. Can the machine be operated using those switches?

 

[Mobiltech]

Those are backup switches to run the machine in the event of an ecm failure. You can run it on those but it will be reduced output. I think about 70% of normal.

 

[bsamot69]

I imagine tracing and locating the circuit interruption will be a daunting adventure. I appreciate your help. Without it I was at a standstill .

 

[Nige]

I imagine tracing and locating the circuit interruption will be a daunting adventure.

The best thing I can suggest is to examine the electrical schematic and identify how many intermediate connectors each wire passes through. Then split the harness at these points and test it in sections.

Personally I would test each potentially defective wire by supplying batt+ via a 5A test light to one end and connecting the other end to machine frame ground. If a wire will pass 5A it can be considered good.

Regarding connectors between the throttle switch and the ECM I see CONN 57, CONN 53, and CONN 16.

 

[bsamot69]

I am going to text the individual circuits. I have a question about the cat diagrams. Following the wires from ecm, say, there is a blue line that leads to set of connections. This is prevalent through entire schematic. What are those indicating?

 

[Nige]

I have a question about the cat diagrams. Following the wires from ecm, say, there is a blue line that leads to set of connections. This is prevalent through entire schematic. What are those indicating?

Somewhere on the schematic (try the bottom RH corner first) there will be a table titled “wire colour descriptions”. That table contains all the answers. It never ceases to amaze me that hardly anybody ever sees it.

 

[Simon C]

I don't have the interactive Schematic for that particular unit, but there is even a pictorial in the schematics that shows exactly where a Certain Connector ( On the schematic will be written Conn.6 or maybe Conn 13) is on the machine. Schematic tells the number of wires in a plug and the coulour of the wires entering and exiting the plug in. Once you know that a wire is surrounded by two blue wires on one side and a red/blue on the other side for example it is easier to figure out with plug in apart what is what.
I like to take a picture of the plug in on the schematic that I want to take apart with my phone and then can look at the picture to figure out what is what.
As Nige said do the 5 amp light test of any wire from one end to another and you will have a way better idea about what is going on.
Simon C