MAP Sensor Circuit Malfunction
The ISUZU-P0105 (Isuzu) diesel fault code means: MAP Sensor Circuit Malfunction. This is a moderate severity code.
- Keep driving?
- Short distances only
- 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
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?
Estimated 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.
Mechanics Guide Step-by-step diagnosis
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.
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- SAE J1939-73Application Layer: Diagnostics (defines the SPN/FMI fault-identifier framework)
- SAE J2012Diagnostic Trouble Code Definitions (defines P0105 as a generic OBD-II code)
P0105 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:
Commonly Affected Vehicles
- Isuzu NPR / NPR-HD with 4HK1 5.2L
- Isuzu NPR-XD / NQR with 4HK1 5.2L
- Isuzu NRR with 4HK1 / 6HK1
- Isuzu FTR / FVR medium-duty with 6HK1 7.8L
- Chevrolet / GMC 4500 / 5500 (Isuzu-chassis) with 4HK1
- Isuzu NPR-ECO-MAX with 3.0L 4JJ1
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