Diagnosing Chrysler transmission max line pressure and P0933, P0869, P1745 codes - Transmission Digest

Diagnosing Chrysler transmission max line pressure and P0933, P0869, P1745 codes

This article applies to Chrysler RFE, RLE and TES transmissions that utilize pressure control solenoids (PCS) for line pressure control. The subject is a rather common electrical fault that may occur on the PCS line pressure solenoid circuit, which results in max line pressure. Diagnosis and correction of a max line pressure condition may become extremely frustrating both in time and dollars spent — going down the rabbit hole, as we call it.

Surprisingly, there is no Chrysler code for a circuit fault with PCS line pressure solenoids. The vehicle may contain codes P0933, P0869 or P1745. Let’s examine the code descriptions.

P0933 – Line Pressure Sensor Performance

If the actual line pressure reading is more than 172.4 kPa (25 PSI) higher than the desired line pressure, but is less than the highest line pressure ever used in the current gear, P0933 sets.

Careful! With a max line condition, this code may incorrectly send you to the line pressure sensor.

P0869 – High Line Pressure

If the actual line pressure is consistently higher than the highest desired line pressure ever used in the current gear, high line pressure P0869 will set. P0869 does mention a possible open circuit fault for PCS line pressure solenoid.

Careful! Historically, this code on the 62TE is often a bad powertrain control module (PCM).

P1745 – Line Pressure Too High for Too Long

This code is for the 42RLE and 62TE transmissions only, and typically requires the “Clear Variable Line Pressure (VLP) Counters” procedure to be performed with a scanner under miscellaneous functions.

Read more columns from the TASC Force Tips series here.

Diagnosis

To the point, if you are working on a vehicle that is experiencing actual line pressure (PSI) max pressure of 150–160 PSI at idle in Park, Neutral and Drive ranges and 250 PSI in Reverse, this may be an indication of an open circuit for PCS line pressure solenoid. First, examine scanner data and verify the condition.

Figure 1 is an example of an open circuit via scanner info. Notice in the data that line pressure duty cycle is 38.38%, line pressure is 160 PSI and the desired line pressure is default (125 PSI) with no activity. If your scanner supports it, try bidirectional control of PCS solenoid and line pressure.

Figure-1-Open-Circuit-1400
Figure 1.

Circuit Analysis

Figure 2 shows a 2013 Dodge Ram with a 6.7L diesel engine and the 68RFE transmission. This era of vehicle is extremely prone to the condition of an open circuit and max line pressure. Pay attention, as this condition may either be intermittent, or happen all the time.

Important: Your system may be different. Secure a wiring diagram for your VIN.

Figure-2-PCM-Ground-Control-Circuit-1400
Figure 2.

To test this circuit, use your choice of electronic test instrument with a low-current clamp on the PCS ground control wire #12 to PCM C1 terminal pin 29. Open the wiring conduit and locate the correct wire. Clear codes and monitor the circuit KOER in Park or Drive range; current flow varies from 0.20 to 1.00 amps. When current flow is observed, that is verification that it is not an open circuit. This circuit with a short to ground will also have current flow, but that is the opposite: a low-pressure condition. The amp test above is a non-invasive diagnostic tool that is useful when using scope for an intermittent condition.

Tech Tips

If other solenoids are functional and if code P0882 is not present (low voltage supply), the power supply side of the circuit is usually not at fault.

Your PCS line pressure control may look different. 42RLE, 40TES and 41TES transmissions have the solenoid separate from solenoid pack.

At times, max line pressure may be mistaken for aftermarket tuning. The difference is that tuning may have higher max pressure than 160 PSI and it will not flatline with no activity like a circuit issue.
For 62TE, the open circuit is commonly the PCM internally.

Line pressure duty cycle is not available on all scanners for 62TE, 40TES, 41TES and 42RLE.

Summary

I leave you today with a quote from Mr. Robert Kenny Jr., an automotive instructor at Hudson Valley Community College: “The cost for a lack of education far exceeds the cost of an education.”

Jim Mobley is a Sonnax technical communication specialist. He is a member of the Sonnax TASC Force (Technical Automotive Specialties Committee), a group of recognized industry technical specialists, transmission rebuilders and Sonnax Transmission Company technicians.

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