CAT Engine 22 Fault Code: Cylinder #2 Injector : Erratic, Intermittent, or Incorrect
Also called Cylinder #2 Injectior : Erratic, Intermittent, or Incorrect, Cylinder #2 Injector - Erratic, Intermittent, or Incorrect, Cylinder #2 Injector Erratic, Intermittent, or Incorrect, Cylinder #2 Injector erratic, intermittent, or incorrect, Engine Injector Cylinder #02 : Erratic, Intermittent or Incorrect, Engine Injector Cylinder #02 : Erratic, Intermittent, or Incorrect
Cylinder #2 Injector : Erratic, Intermittent, or Incorrect · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault code 22 (SPN 652 / FMI 2) on CAT C175 engines means the ECM detected that data from the No. 2 cylinder electronic unit injector is out of limits. The engine will derate while this code is active, so it needs prompt attention even though it is not an immediate shutdown event.
High severity. The engine will be derated while this code is active, which means reduced power and possible operational limits until it is fixed. It is not listed as an immediate engine-damage or shutdown code, but ignoring a derate for long periods affects productivity and can mask a worsening electrical or injector fault.
What does CAT Engine error code 22 mean?
Fault code 22 is triggered when the ECM sees data from the No. 2 cylinder's electronic unit injector that falls outside expected limits. Each injector on the C175 shares a power supply circuit with another injector but has its own individual return (ground) circuit back to the ECM, except on the C175-20 engine where cylinders 9, 10, 19, and 20 have individual circuits for both power and return.
Because injectors share power circuits, a short circuit to ground on the return line of a paired injector can sometimes cause the ECM to log a fault on the injector that isn't actually the problem. This is why CAT's troubleshooting relies on the Injector Solenoid Test, which briefly activates each solenoid with the engine off and reports its status as OK, Open, or Short.
When this code is active, the ECM logs it, generates a warning on the control panel or a warning light (depending on the machine's setup), and derates the engine until the fault is resolved.
What triggers a CAT Engine 22 code?
The ECM sets this code when data from the No. 2 cylinder electronic unit injector is out of limits, and only if none of the following related codes are active: diagnostic code 0168-01, diagnostic codes 0002-05 and 0002-06, any 0041 diagnostic codes, any 0262 diagnostic codes, diagnostic code 0190-08, and any 0110 diagnostic codes.
Common causes of 22
- Leakage at the injector or fuel system connections
- Damaged connectors and/or wiring, including problems that only show up under vibration
- A short circuit detected in the injector solenoid circuit (supply or return line)
- An open circuit in the injector solenoid circuit (supply or return line)
- A problem with the ECM itself, including a bad or disconnected ECM
- A problem with the wiring harness, including the external engine harness
- Resistance in the return wires
- A faulty No. 2 cylinder injector
How to troubleshoot CAT Engine 22: first checks
- With the engine off, run the Injector Solenoid Test to activate each solenoid briefly. Listen for an audible click and check whether the tool reports the No. 2 injector circuit as OK, Open, or Short.
- Inspect connectors and wiring at the No. 2 injector and along the shared power supply circuit for corrosion, damage, or loose pins, paying attention to points that could be affected by engine vibration.
- Check whether any of the related diagnostic codes (0168-01, 0002-05, 0002-06, 0041, 0262, 0190-08, 0110) are active, since these must be inactive for code 22 to be valid and can point to a different root cause.
- Because injectors share a power supply circuit in pairs, check the paired injector's return line for a short to ground, since this can cause a fault to log on the No. 2 injector even though the actual short is elsewhere.
- Verify ECM connections are secure and that the ECM has not been disconnected or is not faulty.
- If an injector was recently replaced, confirm the correct injector trim code was programmed into the ECM.
How the code clears
No separate clearing step is listed beyond correcting the underlying cause. Since the engine is derated while the code is active, expect normal power to return once the faulty injector, wiring, or ECM issue is repaired and the code is no longer active. If an injector or the ECM itself is replaced, the injector trim codes must be reprogrammed into the ECM.
Affected models and serial ranges
22 appears in our records across 1 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C175 | Serial range not listed in source records |
Frequently asked questions
What does CAT fault code 22 mean?
It means the ECM detected that data from the No. 2 cylinder electronic unit injector is out of limits. This is specific to CAT C175 engines and corresponds to SPN 652, FMI 2.
Will fault code 22 shut down my engine?
No shutdown is listed. Instead, the engine will be derated (reduced power) while the code is active, and a warning will appear on the display or warning light depending on the machine.
Can a wiring problem cause code 22 even if the injector is good?
Yes. Because injectors share a power supply circuit in pairs, a short circuit to ground on the return line of the paired injector can cause the ECM to log the fault on the No. 2 injector even though that injector is functioning normally. The Injector Solenoid Test helps isolate which circuit is actually at fault.
What is the Injector Solenoid Test and how do I run it?
It's a diagnostic test performed with the engine off that briefly activates each injector solenoid one at a time. A good solenoid makes an audible click, and the test reports each circuit's status as OK, Open, or Short.
Do I need to reprogram anything after replacing an injector?
Yes. When you replace an injector on the C175, you must program the new injector's trim code into the ECM. If you replace the ECM itself, all injector trim codes for every cylinder must be reprogrammed.
Are there other codes I should check before assuming it's the No. 2 injector?
Yes. The ECM only sets code 22 if diagnostic code 0168-01, diagnostic codes 0002-05 and 0002-06, any 0041 codes, any 0262 codes, diagnostic code 0190-08, and any 0110 codes are not active. If any of those are active, they may be the real underlying issue.
Is cylinder 2 different on the C175-20 engine?
The C175-20 engine has a general design note that cylinders 9, 10, 19, and 20 do not share a paired power supply circuit, they have individual power and return circuits. Cylinder 2 itself follows the standard shared power supply, individual return design.