Choose the reference for the question
Use a supplied identity record, document register and diagram cross-reference to select the applicable information, and preserve any unresolved conflict before diagnosis.
The short version
- Match model, specification, controller revision and document scope before using a pin label.
- An operating guide, parts list and service diagram answer different questions.
- A page number without its document identity and revision is an incomplete reference.
A diagram is a claim about a particular unit
You already have a readable label. Now the question is whether the page on the bench describes the installed controller.
Our fictional RP-B12-C label is C-2034. The supplied controller record says R2; a loose diagram says R1.
Do not solve that conflict by picking the newer-looking page. First identify what each document covers.
| Supplied record | Meaning |
|---|---|
| Unit | RP-B12-C / C-2034 |
| Controller record | R2 installed |
| Loose diagram | R1 circuit |
| Decision needed | Which reference applies? |
Choose the document that answers the task
An operator guide explains use; a parts list identifies assemblies; a service document may describe diagnosis. Their purposes are different.
Cummins lists related literature separately and identifies its generator by model and specification. That is a real example of checking document purpose and identity.
It does not make a Cummins document applicable to this fictional controller. Here, the training register supplies the required scope.
| Document | Question it can support |
|---|---|
| Operator guide | Use and operator information |
| Parts list | Assembly identity |
| Service document | Applicable diagnostic information |
| Training register | Scope of this invented exercise |
Read every applicability condition
The training register lists D1 for controller R1, regardless of the coach appearance. D2 covers R2 in serial range C-2000 through C-2499.
C-2034 and R2 satisfy both D2 conditions. D3 covers R2 only from C-2500, so its later date is irrelevant here.
The register marks D2 revision 3 current for this example. In real work, check the manufacturer source and applicable superseding instructions.
| Training document | Applicability |
|---|---|
| D1 / revision 5 | R1 only |
| D2 / revision 3 | R2, C-2000 to C-2499 |
| D3 / revision 4 | R2, C-2500 onward |
Follow the page reference, not a thumbnail
D2 page 2 sends the request-input question to sheet E2. E2 carries the same document ID and revision in its title block.
A thumbnail labeled furnace wiring lacks that identity. It cannot replace the complete document and its cautions.
Keep the reference chain: unit record, controller revision, document revision, sheet, connector and pin.
Keep a conflict visible
The loose R1 page shows a request on J2.4. D2 sheet E2 assigns the request to J2.2. Those labels cannot be combined.
Record the loose page as conflicting material. Do not declare it universally obsolete or quietly erase it from the job history.
If the controller revision were unreadable, the correct next step would be to obtain it or ask the qualified lead, not guess a pin.
| Supplied record | Meaning |
|---|---|
| R1 loose page | J2.4 request |
| Matched R2 document | J2.2 request |
| Do not do | Mix the two pin maps |
| Unknown revision | Request identity evidence |
Try the decision before the answer
A second unit is C-2601 with controller R2. Which reference in the same register would you choose?
D3 fits its serial range. Selecting D2 because it worked on the first unit would copy a valid reference onto an invalid application.
A matching drawing still does not prove that a request signal exists, that a wire is sound or that a controller has failed.
| Supplied record | Meaning |
|---|---|
| New unit | C-2601 / R2 |
| Supported reference | D3 / revision 4 |
| Still unknown | Actual circuit condition |
Write a usable reference trail
Write: RP-B12-C, C-2034, controller R2; training D2 revision 3, sheet E2, J2.2 request. Conflicting R1 loose sheet retained for review.
That note establishes the reference used. It does not claim a diagnosis, safe access, a completed test or permission to work.
Next, practice selecting the reference in the case, then use the request-signal diagram activity to separate identity from circuit evidence.
| Supplied record | Meaning |
|---|---|
| Known | Identity and applicable page |
| Conflict | R1 loose sheet retained |
| Not yet known | Request signal or fault |
| Next practice | Reference case and request diagram |
Carry the context into the circuit
Before reading a wire or pin, carry the unit identity and document revision with it.
Use the drawing legend and operating state on that page. Stop when a required identifier or cross-reference is missing.
This is desk reasoning with original examples. Field work still requires the actual manufacturer procedure and a qualified person.
Shop tip
Josh: Say what the reference lets you conclude, then name the question it cannot answer.
Where this comes from
- Cummins Onan HGJBB (Spec A-B) Operator Manual A031C171; Issue 8, December 2018; printed 9-10 (PDF 15-16), related literature and model identification; checked 2026-11-04. Scope: Identity and document-purpose example only; no generator service procedure or specification is taught. https://www.cummins.com/sites/default/files/rv-manuals/A031C171.pdf
- Original Rigprobe teaching examples, 2026-11-04. Identifiers, diagrams, connector layouts, timings and readings are invented problem data, not OEM drawings, specifications or universal acceptance limits.
Try it on a service call
Put the lesson to work on a hands-on troubleshooting case.