Code
P1600
SATURN
P — Powertrain
PCM Battery
Views:
UK: 31
EN: 37
RU: 29
AI status
Completed
Completed
100%
Causes
- Weak, discharged, or dead vehicle battery
- Corroded, loose or damaged battery terminals/cables
- Poor or missing battery negative/ground connection
- Blown fuse or fusible link supplying PCM B+ or IGN power
- Ignition switch or relay faults that remove PCM power
- Faulty charging system (alternator)
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Stored and recurring DTCs or loss of learned values
- No‑start or hard starting (if PCM loses memory or supply)
- Intermittent stalling or odd driveability complaints
- Some electrical systems may behave unpredictably
What to check
- Retrieve freeze frame and full DTC list with a scan tool; note code history
- Visually inspect battery, terminals, cable condition and clamp tightness
- Check and load test battery state of charge and capacity
- Measure battery voltage: key off, key on, and during cranking
- Inspect fuses/fusible links and ignition relays feeding PCM
- Verify PCM constant B+ and ignition-switched power pins for proper voltage
Signal parameters
- Battery/resting voltage (key off): ≈12.4–12.8 V (fully charged ~12.6 V)
- Ignition on (key run): ≈Battery voltage (no significant drop)
- Charging system voltage (engine running): ≈13.5–14.8 V
- Cranking voltage: typically should remain above ≈9.0–10.0 V (varies by spec)
- PCM B+/constant power pin: battery voltage present at all times
- PCM switched/IGN power pin: battery voltage when key ON
Diagnostic algorithm
- Read and record all codes, freeze frame and stored data. Note whether P1600 is current or history.
- Visually inspect battery, cables and chassis/engine grounds. Clean and tighten terminals if corroded or loose.
- Measure battery voltage with key off. If below ~12.2 V, charge battery and perform a battery load/health test; replace if failing.
- With a known good battery or charged battery, check voltage at PCM constant B+ and ignition power pins. Compare to battery posts.
- Check cranking and charging voltages. Repair charging system faults before proceeding.
- Inspect and test fuses/fusible links and ignition relays that supply the PCM. Replace any faulted items.
- Perform continuity checks on power and ground circuits between battery, fuse box, and PCM. Repair any opens/corrosion.
- Clear codes, reconnect and cyclically test vehicle (key cycles and engine run). See if P1600 returns.
- If wiring, battery and charging system are good and code returns, consider PCM internal fault. Verify software/flash level and consider reprogramming or replacement per manufacturer procedure.
- After repairs, perform full drive cycle and confirm code does not reappear.
Likely causes
- Low battery state of charge or failing battery
- Loose/corroded battery terminals or bad ground
- Blown/loose fuse feeding PCM constant power
- Intermittent wiring or connector fault to PCM power pins
Fault status
Status
PCM Battery — indicates irregular or missing power supply to the PCM or a fault with the PCM's keep‑alive memory. Check battery, cables, fuses and PCM power/ground circuits; replace or reprogram PCM only after verifying external power/wiring are correct.
Repair difficulty: Medium
Diagnostic time: 0.5-3 hours
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