2011 C70 ECM-304C, ECM-950C, ECM-21CC | SwedeSpeed

This is VIDA info for each code. Inspect for an intake leak after the AMM. It will be hard to locate without a smoke test. You could have a dirty throttle plate that needs to be cleaned. ECM-21CC and 950C are probably related to the same fuel trim issue. Don’t know what to tell you about the knock sensor code except for VIDA info. It is very rare to have a knock code on any Volvo. The engine itself is probably not causing the knock code. After erasing codes, remove the battery cables and touch the cables ends together for 10 seconds. This will erase any old adaptive learned memory. Sometimes the ECM will set a ghost code from old RAM until the old memory flushes out. There will be a big spark when removing the first battery cable and installing the last battery cable. This is normal for all P1’s, I do not know why.
Has the PCV been replaced, the pcv diaphragm will split open causing a high-pitched noise at idle. Engine at idle, remove the oil cap or dipstick. If the noise goes away, replace the pcv box or diaphragm.
See fcpeuro and IPD info for pcv repair if the above test is true.

ECM-21CC Long-term fuel trim, idling, bank 1. Upper limit, B5254T7
Diagnostic trouble code (DTC) information ECM-21CC
Condition
The engine control module (ECM) receives information from the heated oxygen sensor (HO2S) about the fuel / air mixture. If the fuel / air mixture deviates from λ=1, the short-term fuel trim will compensate for this by adjusting the injection time so that λ=1 is achieved. When the short-term fuel trim makes an adjustment, the integrator median must be adjusted by the long-term trim. The diagnostic trouble code (DTC) will be stored when the long-term trim must be adjusted almost to maximum in the idle range.
The diagnostic trouble code (DTC) can be diagnosed when idling.
Substitute value
None.
Possible source
Too high ethanol content in fuel.
Air leakage in the intake system
Damaged heated oxygen sensor (HO2S).
Fault symptom
Malfunction indicator lamp (MIL) lit.

ECM-950C Engine control module (ECM), idle speed control. Signal too high, B5254T7
Diagnostic trouble code (DTC) information ECM-950C
Condition
If Engine Control Module (ECM) registers that the actual idle rpm (actual value) is over the limit value for a certain time, the diagnostic trouble code (DTC) is generated.
Substitute value
None.
Possible source
Air leakage in the intake system.
Fault symptom
Malfunction indicator light (MIL), on
High idle speed
Uneven idle

ECM-304C Rear knock sensor (KS). Signal too high, B5254T7
Diagnostic trouble code (DTC) information ECM-304C
Condition
In certain operating conditions the engine control module (ECM) checks the signal from the rear knock sensor (KS). The diagnostic trouble code (DTC) is stored if the signal from the rear knock sensor (KS) is too high in these operating conditions.
The diagnostic trouble code (DTC) can be diagnosed when the engine is running.
Substitute value
Safety retardation of ignition advance
Reduced boost pressure.
Possible source
Short-circuit to ground in the signal cable
Incorrectly installed knock sensor (KS)
Damaged temperature sensor.
Fault symptom
Poor performance.

Volvo Ignition Coil Connector Terminal Pin – Genuine Volvo 978262 | FCP Euro

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