John Deere Engines SPN443 Fault Code: Auxiliary Gauge Pressure #2 Reading Extremely High
Auxiliary Gauge Pressure #2 Reading Extremely High · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 443 sets when the engine control unit sees the EGR temperature signal reading much higher than expected for current operating conditions, with the engine running for at least 3 minutes. The alarm level is Stop, so treat it as a serious exhaust and EGR system fault, not a nuisance code.
High severity. The listed alarm level is Stop, meaning John Deere classifies this as a condition serious enough to warrant shutting the engine down rather than continuing to operate. Because it ties into EGR temperature and exhaust flow, ignoring it risks turbocharger, EGR valve, or exhaust system damage.
What does John Deere Engines error code SPN443 mean?
SPN 443 relates to an auxiliary gauge pressure reading described as extremely high, and the diagnostic detail tied to this code centers on the EGR temperature signal reading much higher than expected for the engine's current operating conditions. The EGR (exhaust gas recirculation) system routes a portion of exhaust gas back into the intake to reduce combustion temperatures and emissions, and it relies on accurate temperature and flow readings to work safely.
When the ECU sees a temperature signal that does not match what the engine's operating state should produce, it flags this fault because it can no longer trust that the EGR system, turbocharger, and related exhaust components are behaving as designed. The control unit responds by trying to maintain proper operating conditions, but a persistent extreme reading suggests something in the EGR, exhaust, or turbocharger circuit needs physical inspection.
This code does not stand alone. John Deere lists a long troubleshooting sequence of related SPNs and FMIs covering coolant temperature, EGR flow and position sensors, boost pressure, and turbocharger actuator circuits, meaning a technician working this fault should expect to check several connected systems, not just one sensor.
What triggers a John Deere Engines SPN443 code?
The DTC becomes active only when the engine has been running for a minimum of 3 minutes and the EGR temperature signal shows a much higher reading than expected for the operating conditions present at that time.
Common causes of SPN443
- Loose fan belt
- Damaged fan shroud
- EGR flow sensor venturi with a loose bracket
- Low coolant level
- Bad terminals or connector at the EGR temperature sensor
- Bad EGR temperature sensor
- Open or shorted harness
- Bad ECU software
- Bad ECU
- Bad terminals or connector at the ECU
- VGT (variable geometry turbocharger) vanes sticking
- Plugged EGR circuit
- EGR system leak
- Exhaust leak
- EGR flow sensor restriction
- Exhaust restriction
- Damaged turbocharger
- VGT vane position sensor inaccurate
How to troubleshoot John Deere Engines SPN443: first checks
- Inspect the fan belt for looseness and the fan shroud for visible damage before digging into electrical diagnostics.
- Check coolant level and top off if low, since low coolant can throw off temperature readings the ECU relies on.
- Inspect the EGR flow sensor venturi and its mounting bracket for looseness or shifting.
- Check terminals and connectors at both the EGR temperature sensor and the ECU for corrosion, looseness, or damage.
- Look over the wiring harness between the EGR temperature sensor and ECU for signs of chafing, shorts, or opens.
- Inspect the EGR circuit and exhaust system for leaks, restrictions, or plugging that could distort temperature readings.
- Check the turbocharger for damage and confirm the VGT vanes move freely rather than sticking, since a sticking VGT can affect exhaust temperature and pressure behavior.
How the code clears
No separate clearing step is listed for this code beyond correcting the underlying cause. Because the alarm level is Stop, the fault should be diagnosed and repaired before returning the engine to normal service. For the actual diagnostic procedure and step-by-step checks, John Deere directs technicians to the application technical manual for the specific engine and machine.
Frequently asked questions
What does SPN 443 mean on a John Deere engine?
It means the ECU detected an EGR temperature signal reading much higher than expected for the engine's current operating conditions, after the engine had been running for at least 3 minutes. Description text also references an auxiliary gauge pressure reading extremely high.
Is SPN 443 serious enough to stop the engine?
John Deere lists the alarm level for this code as Stop, which means yes, it is treated as a fault serious enough to warrant shutting down rather than continuing to run the engine.
What are the most common causes of SPN 443?
John Deere lists eighteen possible causes ranging from a loose fan belt and damaged fan shroud to a bad EGR temperature sensor, exhaust or EGR leaks, restrictions, a sticking VGT, or a bad ECU. There is no single most likely cause named, so checking mechanical items like belts, coolant level, and connectors first is a practical starting point.
Can low coolant cause this fault code?
Yes, low coolant level is listed as one of the possible causes, likely because it affects the operating conditions the ECU uses to judge whether the EGR temperature reading makes sense.
Does SPN 443 point to a bad EGR temperature sensor specifically?
It can. Bad terminals or connectors at the EGR temperature sensor and a bad EGR temperature sensor itself are both listed causes, but so are harness problems, ECU issues, and mechanical exhaust or turbocharger problems, so the sensor should be checked as part of a broader inspection, not assumed as the sole cause.
What other codes should I check alongside SPN 443?
John Deere's troubleshooting sequence for this code lists a long set of related SPNs and FMIs covering coolant temperature (SPN 110), intake or boost related sensors (SPN 102, SPN 108, SPN 1209), turbocharger actuator circuits (SPN 2659), and several others, indicating this fault should be diagnosed alongside those related codes rather than in isolation.
Where do I find the actual repair steps for SPN 443?
John Deere does not provide the detailed diagnostic procedure in the general fault code reference. It directs technicians to the application technical manual for the specific engine and machine for the full step-by-step diagnostic procedure.