MAP Sensor Circuit High
The ISUZU-P0108 (Isuzu) diesel fault code means: MAP Sensor Circuit High. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- intermediate
- Estimated cost
- $200-$2,800
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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)
- Contaminated MAF sensor from oiled aftermarket filter or soot blow-by Likely
- VGT / VNT actuator carbon-lock on 4HK1 / 6HK1 turbo Likely
- Intake boot or CAC hose leaking near clamp Possible
- EGR valve stuck open leaking soot into intake stream Possible
- Sensor wiring chafe near hot turbo / valve cover Possible
Step-by-Step Diagnostic Procedure
Connect IDSS (Isuzu) or Tech2 (GM-badged NPR) and verify P0108 with freeze frame. Compare MAF actual vs calculated airflow at idle and snap-accel.
Inspect intake tract end-to-end for loose clamps, split hoses, and cracked CAC — pressure-test with a smoke machine.
Remove VGT actuator and verify free vane sweep — ACERT-style carbon lock is common on 6HK1 with high idle hours.
Replace MAF only after cleaning first (CRC MAF cleaner); oiled filters coat the wire and create chronic P0101.
If VGT is commanded but boost lags, check for wastegate actuator rod movement and vacuum/electrical feed integrity.
Frequently Asked Questions
What does Isuzu code P0108 mean?
Isuzu diagnostic trouble code P0108 (MAP Sensor Circuit High) 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 P0108?
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 P0108?
Typical repair cost runs $200-$2,800. Sensor, wiring, and DEF-related repairs fall at the low end; DPF service, turbo, injector, and EGR cooler work fall at the high end and may require dealer-level programming.
Sources
This page is built from documented references. Verify against your own service info before repair work.
P0108 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown: