MAP Sensor Circuit Malfunction
The ISUZU-P0105 (Isuzu) diesel fault code means: MAP Sensor Circuit Malfunction. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- intermediate
- Estimated cost
- $100-$500
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Common Symptoms
- Loss of power, sluggish acceleration
- Black smoke under load
- Poor fuel economy
- Irregular idle
- Check Engine Light with possible derate
Probable Causes (Ranked by Likelihood)
- Failed MAP/boost pressure sensor (Isuzu 8-98009-418-0 on 4HK1/6HK1) Likely
- Open or short in the MAP sensor signal wire, or signal shorted to the 5V reference Likely
- Corroded or loose sensor connector terminals (engine-bay heat and vibration on cab-over trucks) Possible
- Missing or unstable 5V reference or sensor ground from the ECM Possible
- Sensor port or vacuum passage plugged with soot/oil residue causing implausible signal Possible
Step-by-Step Diagnostic Procedure
Connect IDSS (Isuzu) or Tech2 (GM-badged NPR), confirm P0105 with freeze frame, and compare the MAP/boost pressure reading key-on-engine-off against barometric pressure — they should match within about 1 psi at rest.
Inspect the MAP/boost sensor connector on the intake manifold for corroded, spread, or backed-out terminals; wiggle-test the harness while watching live sensor voltage.
With the connector unplugged, verify the 5V reference and sensor ground at the connector with key on. No 5V points to a harness open/short or ECM feed problem.
Check signal-wire continuity from the sensor connector to the ECM and check for shorts to ground or to the 5V reference (a signal stuck near 4.5-5V with no vacuum applied indicates a short to reference or a failed sensor).
If wiring, reference, and ground all check good, replace the MAP/boost pressure sensor, clear the code, and verify the reading tracks boost under a loaded road test.
Frequently Asked Questions
What does Isuzu code P0105 mean?
Isuzu diagnostic trouble code P0105 (MAP Sensor Circuit Malfunction) is a moderate-severity fault on Isuzu medium-duty diesel engines. It indicates a problem in the air/boost system that should be verified with a scan tool (Isuzu IDSS / Tech2 for Isuzu) before replacing any parts.
Can I drive my Isuzu truck with P0105?
Short runs may be possible but do not ignore — Isuzu medium-duty aftertreatment faults cascade quickly into 5-mph derate or no-restart. Schedule diagnosis immediately.
How much does it cost to fix Isuzu P0105?
Typical repair cost runs $100-$500. The MAP/boost pressure sensor itself is inexpensive ($30-$150 aftermarket, more for OEM 8-98009-418-0); most of the cost is diagnostic time and any harness/connector repair. No dealer programming is normally required.
Sources
This page is built from documented references. Verify against your own service info before repair work.
P0105 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown: