FANUC 0i-TF Plus Multi-Step Skip J849: what PS0370 after G31 P3 actually tells you

If ordinary G31 works but adding P3 produces PS0370, neither a failed probe nor a missing purchased option has yet been proved. Save the complete alarm and offending block, then identify the control generation. This article concerns 0i-TF Plus; its Plus-series ordering code must not be transferred to 0i-TD.

What J849 covers

Page 177 of FANUC's 2024 Plus Series function catalogue lists A02B-0349-J849 as 0i-TF Plus Multi-Step Skip. It identifies the function as basic on 0i-MF Plus and requires Custom Macro B to access the stored coordinate variables. Retain the complete ordering prefix when checking a system. The sources do not establish one minimum software version for every installation; FANUC or the machine builder must confirm eligibility against the CNC model and software series/version.

Multi-Step Skip lets a program use different skip conditions at different process stages. G31 P1–P4 provide skip movement; G04 Q1–Q4 provide skippable dwell. A valid signal records position and cancels the remaining movement in the former case, or cancels remaining dwell in the latter. This is process control, not an emergency-stop or collision-protection function.

Read the block before ordering an option

Connection manual B-64693EN-1/01, printed page 2469, names the alarm PS0370 — G31P/G04Q ERROR. For the multi-step commands discussed here, check three branches:

• The G31 P value is outside 1–4.
• The G04 Q value is outside 1–4.
• P1–P4 or Q1–Q4 was used without Multi-Step Skip.

The same entry includes P conditions for particular T-series G72/G74 grinding cycles. Do not transfer those conditions to every turning cycle with the same number. An identical alarm number does not make the command context identical.

For example, a block intended to select the third condition but written as G31 P5 first presents a program-value problem. If the complete block uses P3, checking the installed function becomes the next branch. This is a diagnostic illustration, not a reported field repair.

P3 does not mean physical input number three

G31 P3 and G04 Q3 are format fragments, not executable sample programs. The move requires reviewed axes, destination and feed; the dwell requires conditions specified in the machine's manual. P/Q select a configured skip condition. Check the builder's wiring and parameter records rather than connecting a wire simply because it is labelled input three.

For the conventional input path, also check that the signal resets before the next block. The documented state monitoring can immediately satisfy the next condition if the signal remains active. Do not mistake this for a block being ignored, or generalize it into an edge rule for every high-speed input.

Separate activation from commissioning

1. Provide FANUC or the builder with the full CNC model, software version, installed-option list, measuring device and program fragment. Ask them to confirm suitability, dependencies and whether an additional licence is needed.
2. If a function must be added, obtain the machine-specific activation procedure through the authorized service channel. A public catalogue confirms ordering information, not a universal certificate-import procedure; no cross-model installation sequence has been verified here.
3. After activation, have the builder verify the interface, input mapping and measurement logic. Changing signal parameters does not grant an option licence.
4. Qualified personnel should validate the installation without a workpiece collision risk, testing active, absent and non-reset signals separately and confirming the recorded position.

Before motion, verify the effective feed source and the conditions governing override, dry run and acceleration/deceleration. They cannot be assumed to behave like ordinary cutting blocks during skip operation. Allow probe overtravel and stopping distance; do not use the measuring signal as a safety circuit.

Sources and applicability

FANUC 2024 Plus Series Function Catalogue, p. 177 supports the feature, ordering code and dependency. FANUC B-64693EN-1/01, §15.3.5, printed pp. 2461–2469, third-party mirror supplies command, signal and alarm conditions. Use the builder's documents and the manual matching the installed software for implementation.