Kyle Alexander

So, I recently bought a 2009 LNF and have been troubleshooting ever since getting it... I'm currently throwing a P2096 code. The only mod I can see is a ZZP Interooler and what I can only assume is a Stage 1 tune due to a stock ECM and 3-bar MAPs. The car has been losing boost power while driving and has now started to buck and stutter again. I recently replaced the plugs and coils which seemed to resolve the stuttering problem, but it has now come back. I have also replaced the purge solenoid, changed the oil, and done a boost test (found no leaks).

Any clue how to fix this? I've checked everything, including the intercooler for any signs of leaking. Internet search has shown little help on the CEL code aside from replacing an O2 sensor. However, to my knowledge, this shouldn't be causing the car to buck around. So is it a fuel injector issue? Fuel pump? Faulty MAF? Or is it actually an O2 sensor? I just never trust that answer, because it is typically a bullshit, mechanic's quick fix to a problem.

Any help would be awesome!

umrdyldo

iTrader: (1)

#1 you need a way to monitor the cars sensors. A cheap blutetooth reader etc.
- You really should look and see what your fuel trims are.
#2 Check the exhaust fuse under the hood in the fuse box. Should be labeled EXH
#3 Check the wiring harness that goes from the ECU to the O2 sensors. It runs on the top right side of the engine.
#4 Check the exhaust for leaks near the cat
#5 Replace the rear 02 sensor.

Kyle Alexander

Ok, this code reader is also returning the codes P0122, P0223, P0193, and P0090. First two are throttle controls sensors. Second two are most likely the fuel pump or fuel filter (apparently a complete system on my model...). So it seems as though I'm going to have an expensive repair and got ripped off by the seller.

umrdyldo

iTrader: (1)

Service Information
2008 Chevrolet Cobalt | Cobalt, G5 (VIN A) Service Manual | Document ID: 1957290
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DTC P0087, P0088, or P0089
Diagnostic Instructions
• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors
DTC P0087: Fuel Rail Pressure (FRP) Too Low

DTC P0088: Fuel Rail Pressure (FRP) Too High

DTC P0089: Fuel Pressure Regulator Performance

Circuit/System Description
The fuel rail pressure sensor detects fuel pressure within the fuel rail. The engine control module (ECM) provides a 5-volt reference voltage on the 5-volt reference circuit and ground on the low reference circuit. The ECM receives a varying signal voltage on the signal circuit.

High pressure fuel is regulated by the high pressure fuel pump actuator, which is a part of the high pressure fuel pump. The high pressure fuel pump actuator is a solenoid valve. The ECM provides battery voltage on the actuator high control circuit and ground on the actuator low control circuit. Both circuits are controlled through output drivers within the ECM. When deactivated, both drivers are disabled. When activated, the actuator low control circuit driver connects the low control circuit to ground and the actuator high control circuit driver pulse-width modulates (PWM) the high control circuit.

The high pressure mechanical fuel pump is driven by three lobes on the camshaft. The ECM uses the camshaft and crankshaft position sensor inputs to synchronize the high pressure fuel pump actuator with the position of each of these camshaft lobes. The ECM regulates fuel pressure by adjusting the portion of each pump stroke that provides fuel to the rail.

The ECM creates a feedback loop between the pressure sensor and the high pressure fuel pump actuator. If the difference between expected and actual inputs exceeds a calibrated value, or if the amount of correction exceeds a calibrated value, a DTC sets.

Conditions for Running the DTC
• DTCs P0090, P0091, P0092, P0191, P0192, P0193 are not set.

• The ignition 1 signal parameter is less than 18.1 volts.

• The relative injected fuel mass is between 5.016-500 percent.

• The deceleration fuel cut-off (DFCO) is inactive.

• The engine speed is greater than 25 RPM.

• The engine start temperature is greater than -48°C (-54.4°F)

• The DTCs run continuously when the above conditions are met for 2 seconds.

Conditions for Setting the DTC
P0087
The actual fuel pressure is 1.5 MPa (218 psi) less than the desired fuel pressure.

P0088
The actual fuel pressure is 2 MPa (290 psi) greater than the desired fuel pressure.

P0089
• The fuel pressure adjustment is greater than +2.5 MPa (+363 psi) or less than -2.5 MPa (-363 psi).

• The DTCs set when the above conditions are met for 4 seconds.

Action Taken When the DTC Sets
• DTCs P0087, P0088, and P0089 are Type A DTCs.

• A message center or an indicator displays Reduced Engine Power when DTC P0087 sets.

Conditions for Clearing the DTC
DTCs P0087, P0088, and P0089 are Type A DTCs.

Diagnostic Aids
• A skewed fuel rail fuel pressure sensor may set these DTCs.

• Faulty fuel injectors may set DTCs P0087 or P0089.

Reference Information
Schematic Reference
Engine Controls Schematics

Connector End View Reference
Component Connector End Views

Description and Operation
Fuel System Description

Electrical Information Reference

• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference
Control Module References for scan tool information

Circuit/System Verification
•If any other DTCs are set, perform those diagnostics first.
•Operate the vehicle within the parameters described in Conditions for Running and Conditions for Setting. The DTC should not set this ignition.
⇒ If the DTC sets this ignition, proceed with Circuit/System Testing.

Circuit/System Testing
Important: Circuit/System Verification must be performed first or misdiagnosis may result.

•Verify the correct low side fuel system pressure. Refer to Fuel System Diagnosis.
•Remove the high pressure fuel pump and visually inspect the lobes on the camshaft for wear.
⇒ If the lobes are normal, replace the high pressure fuel pump.

⇒ If the lobes are worn, replace the camshaft.

Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• Fuel Injection Fuel Rail Fuel Pressure Sensor Replacement

• Fuel Pump Module Replacement

• Fuel Pump Replacement

• Intake Camshaft and Valve Lifter Replacement
© 2009 General Motors Corporation. All rights reserved.