Code
P1358
MAZDA
P — Powertrain
Ignition Diagnostic Monitor Signal Out Of Self Test Range
AI status
Completed
Completed
100%
Causes
- Faulty ignition coil(s) or coil pack/module
- Open, short or high-resistance wiring in the coil primary/diagnostic circuit
- Poor or corroded connector pins at coil, harness, or ECU
- Weak or low battery/charging system voltage during self-test
- Faulty engine control module (ECU) or ignition drive circuitry
- Intermittent grounding problem or poor chassis/engine ground
Symptoms
- Check Engine Light (CEL) illuminated
- Rough idle or engine hesitation
- Misfire codes or misfire symptoms (loss of power, stumble)
- Hard starting or intermittent no-start
- Reduced fuel economy and increased emissions
What to check
- Read and record all stored/pending codes and freeze-frame data with a scan tool.
- Check battery voltage and charging system; ensure battery >= 12.4 V at rest and no excessive voltage drop during cranking.
- Perform a visual inspection of ignition coils, connectors, and wiring for damage, corrosion, or oil contamination.
- Verify fuses and ignition-related relays are good.
- Wiggle test harness/connectors while monitoring live ignition signals or checking for intermittent faults.
- Compare coil primary voltages and waveforms across cylinders using an oscilloscope or good-quality lab scope.
Signal parameters
- ECU expects clean primary switching pulses: signal should alternate between near-battery voltage and near 0 V corresponding to coil dwell/drive.
- Primary waveform should be consistent between cylinders and not show excessive noise, droop, or open-circuit behavior.
- Dwell/pulse duration and frequency should correspond to engine speed; the self-test expects specific timing behavior — compare to service manual waveforms.
- Coil primary and secondary resistances must match Mazda service specifications (consult model/engine manual for exact ohms).
- No unexpected voltage spikes, missing pulses, or long high/low periods during the ECU self-test window.
Diagnostic algorithm
- Connect a full-function scan tool, read codes and freeze-frame. Note related codes (misfire, cam/crank).
- Clear codes, perform a test drive or crank/run conditions needed to re-create the DTC and record when it sets.
- Confirm battery and charging system health. Charge or replace battery if voltage is low or unstable.
- Visually inspect and clean coil connectors and harness; reseat connectors and repair damaged wiring or terminals.
- With key on engine off (KOEO) and engine running as required, monitor coil primary voltage at the coil connector using a DVOM or preferably an oscilloscope. Look for proper switching between battery and ground and consistent dwell.
- Use an oscilloscope to compare primary waveforms between cylinders. Identify cylinders with abnormal amplitude, missing pulses, or excessive noise.
- Swap the suspect coil with a known-good coil on another cylinder. If the fault moves, replace the coil.
- If swapping coils doesn't identify the problem, trace and test the coil primary wiring back to the ECU for opens/shorts and check the drive transistor outputs at the ECU connector if service data allows.
- Inspect and test engine and chassis grounds; repair any high-resistance ground connections.
- If wiring and coils check OK, consider ECU/ignition driver failure; consult factory service information for ECU bench tests or replacement procedure. After repairs, clear codes and verify no return of the DTC.
Likely causes
- One or more failed ignition coils or coil driver in the ECU
- Damaged or loose harness connector at the coil(s)
- Short to battery or ground in the coil primary/diagnostic wiring
- Low system voltage during the self-test (weak battery or charging fault)
Fault status
Status
Ignition Diagnostic Monitor — signal out of expected self-test range. Check ignition coils, wiring, connectors, battery/grounds and ECU drive circuits.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email