P1794

Code

NISSAN P — Powertrain

Powertrain Control Module Battery Direct Power Circuit

Brand: NISSAN

Type: P — Powertrain

Views: UK: 23 EN: 65 RU: 47

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Blown main fuse or fusible link supplying PCM B+
Loose, corroded or damaged battery terminals
Poor/loose PCM power connector or corroded pins
Damaged wiring harness between battery and PCM (open, high resistance, short to ground)
Aftermarket electrical mods or improper repairs interfering with main power circuit
Faulty body control module/IPDM or other relay/fuse block feeding PCM

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Intermittent engine stalls, no-crank or no-start conditions
Loss of certain powertrain functions or limp mode
Multiple unrelated codes appearing due to loss of PCM power
Electrical accessories or modules not working correctly

What to check

Read freeze frame and stored/memory codes; note conditions when P1794 set
Visually inspect battery terminals, ground connections and main fuses/fusible links
Inspect PCM power connector and wiring for corrosion, damage, pin push-out or melting
Measure battery resting voltage and charging voltage with engine running
Measure voltage at PCM B+ / power-pin with key OFF, key ON, and during cranking
Check continuity/resistance between battery positive and PCM B+ pin with battery disconnected

Signal parameters

Battery voltage at battery terminals: ~12.4–12.8 V (engine off, charged battery) and ~13.5–14.8 V (engine running)
Battery voltage at PCM B+ pin (Key ON): should be within ~0.2–0.5 V of battery terminal voltage
Voltage during cranking at PCM B+ pin: typically should not drop below ~9.0 V (varies by model)
Voltage drop between battery positive terminal and PCM B+ pin: typically
Resistance between battery positive and PCM B+ (with battery disconnected): near 0 ohms, low milliohm to a few ohms depending on circuit components

Diagnostic algorithm

Verify and record exact vehicle conditions when code set (freeze frame, symptoms)
Visually inspect battery, cable ends, battery tray area, and ensure tight clean connections. Clean or replace as required
Check main fuses/fusible links and replace any blown items. Inspect fuse box for heat damage.
With a digital multimeter, measure battery voltage at battery posts (key off and key on). Compare with voltage at PCM B+ pin. Note any difference.
With battery connected, measure voltage at PCM B+ pin while turning key ON and while cranking. Look for large voltage drops or intermittent loss.
If voltage at PCM B+ is low or intermittent, disconnect battery, then measure continuity/resistance between battery positive post and PCM B+ pin. Repair open/high resistance circuits or short-to-ground as found.
Inspect and back-probe the PCM power connector while gently wiggling harness to reproduce the fault (use proper safety and immobilize vehicle). Repair/replace damaged connectors or wiring.
Check ground connections for PCM and engine block/chassis grounds; clean and tighten to specification.
If wiring and fuses test good, verify upstream modules that feed PCM power (IPDM, main relay). Swap/bench-test relay or inspect module fuses as permitted by service info.
If wiring, fuses and supply modules are confirmed good and issue persists, consult manufacturer service information and consider PCM internal fault; follow proper PCM replacement/programming procedures.
Clear codes and test drive after repair. Re-scan to confirm code does not return and verify freeze frame conditions match corrected state.

Likely causes

Blown main fuse / fusible link to PCM
Loose or corroded battery cable or terminal
Faulty/poor PCM power connector or wiring between battery and PCM
High-resistance connection causing voltage drop to PCM

Fault status

⚠️ Status

PCM battery direct power circuit fault detected — battery feed to PCM is missing, low, intermittent, or shorted.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-2 hours

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P1794 — Powertrain Control Module Battery Direct Power Circuit