What Does P2188 Mean?
The PCM is removing fuel (negative long-term fuel trim) at idle to compensate for a rich condition on Bank 1. The air/fuel mixture contains too much fuel or insufficient air specifically at idle speeds.
Common Causes
35%
Leaking or stuck-open fuel injector(s) on Bank 1
25%
Excessive fuel pressure from faulty pressure regulator
20%
Dirty or contaminated MAF sensor reading high airflow
15%
Failed upstream oxygen sensor providing false lean reading
5%
Restricted air filter or intake obstruction
Diagnostic Steps
1
Step 1: Review fuel trim values at idle; negative LTFT beyond -15% confirms rich condition; compare to higher RPM operation
2
Step 2: Check fuel pressure with gauge; should drop to specification when engine is running (excessive pressure indicates regulator issue)
3
Step 3: Perform injector balance test or monitor individual injector pulse widths to identify leaking or stuck injectors
4
Step 4: Inspect MAF sensor element for contamination or oil; verify sensor output voltage/frequency matches actual airflow
5
Step 5: Check upstream O2 sensor response time and voltage range; should toggle 0.1-0.9V; slow or biased sensor causes rich condition
Estimated Repair Cost
$150 - $900
Parts + labor, varies by vehicle and location
The PCM is removing fuel (negative long-term fuel trim) at idle to compensate for a rich condition on Bank 1. The air/fuel mixture contains too much fuel or insufficient air specifically at idle speeds.
The most common cause of P2188 (System Too Rich at Idle Bank 1) is: Leaking or stuck-open fuel injector(s) on Bank 1
Typical repair costs for P2188 range from $150 to $900, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive but will experience poor fuel economy, rough idle, and black exhaust smoke. Rich conditions can foul spark plugs and damage catalytic converter over time.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2188 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel System
Difficulty
Type
Generic (SAE)
Recommended Tools
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