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2001 Dodge Grand Caravan 3.3L P1388 Code: Auto Shutdown Relay Circuit Failure and Transmission Limp Mode Diagnosis

Model: 2001 Dodge Grand Caravan Fault Code: P1338 Posted: 2009-09-06 12:48

My 2001 Dodge Grand Caravan with a 3.3L engine has recently developed a transmission issue where it enters default mode, only allowing 2nd gear and reverse. After taking it to a garage, the mechanic diagnosed a faulty Transmission Control Module (TCM), which was replaced. The van ran normally for one day before returning to limp mode. I then had my neighbor—also a mechanic—suggest tracing all wiring connections. We removed the TCM, IPM (Intelligent Power Module), and PCM (Powertrain Control Module) and inspected all wires visually. No corrosion, nicks, or damage were found. The transmission fluid was changed about 8 months ago, and the TCM replacement was done with a new unit from the dealer. After reassembly, the van will not start at all. A scan tool now shows code P1388 — 'Automatic Shutdown Relay Control Circuit' fault. I'm seeking clarity on what this circuit does and how to properly test it. Can this relay be bypassed temporarily to get the vehicle started? What are the most common causes of this issue, especially in 2001 Dodge Grand Caravan models? I have already checked all fuses (including the fuse box replaced in October with a dealer-part), confirmed the ASD relay coil has proper contacts (NC closed, NO open), and verified it energizes correctly. However, the vehicle still fails to start. I believe the root issue lies in the transmission safety shutdown circuit, but I don't have access to accurate schematics for these circuits. Can anyone provide guidance on how to verify continuity or identify where the ASD relay should receive power? Is there a known wiring diagram for this system specific to 2001 Dodge Grand Caravan?

Related fault codes

P1338

Comments (5)

Anonymous 2009-09-06 14:56

One of the circuits feeding the Automatic Shutdown (ASD) relay in the fuse box under the hood is likely open. The fuse box itself can corrode internally, especially over time. Wiring damage often occurs when transmission components are removed—this may have contributed to an incorrect diagnosis of a faulty TCM. When ASD circuits fail, the transmission enters limp mode. If you only performed visual inspections without using proper diagnostic tools or schematics, that approach might not be sufficient. Was the replacement TCM new or used? Did you confirm it was the correct model for your 2001 Dodge Grand Caravan? Also, are you using a scan tool to retrieve codes—can the TCM communicate with it during diagnostics?

Anonymous 2009-09-06 16:31

The fuse box was replaced in October with a brand-new unit from the dealer. The transmission was never removed. We initially inspected all wiring visually by stripping tape and checking for corrosion, nicks, or damage—no issues were found. Using AllData schematic diagrams, we tested continuity between the IPM and TCM, from IPM to solenoid/pressure switch assembly, and also verified the transmission safety shutdown relay itself. The new TCM installed was sourced directly from the dealer. Originally, codes were read at a garage using an unknown scan tool. Recently, I noticed two odometer-related codes: P1684 (battery disconnected over 50 starts) and P1388 for the automatic shutdown relay. Given that the vehicle previously started fine, I now believe troubleshooting should focus on the ASD circuits. However, I lack access to accurate schematics for these specific circuits—any help with this would be greatly appreciated. Thank you in advance.

Anonymous 2009-09-06 19:30

Did the issue occur after a specific connector was disconnected or reconnected? Was it at the fuse box or at the TCM? It still sounds like a poor or loose connection—especially if the problem appeared right after reassembly. I’ve seen wiring degrade around 18 inches from the TCM connector, and the harness near the front of the transmission is particularly prone to damage. Try gently wiggling the connectors while attempting to start the vehicle—sometimes this reveals intermittent faults. Have you checked all fuses? It sounds basic, but it’s a good first step. Do you need the correct schematic for the ASD relay circuit? This could be critical for proper diagnosis.

Anonymous 2009-09-07 11:03

The vehicle started normally before. After removing the IPM, TCM, input/output speed sensors, and the two connectors on the PCM, it failed to start. I’ve already checked all fuses—no issues. The ASD relay coil was tested: contacts show proper operation (NC closed, NO open), and energization tests confirm normal function. I will now inspect the wiring in the areas you suggested—especially near the TCM and transmission area—since I did previously wiggle connections during inspection. I suspect I may have made a bad connection worse during reassembly. I’ll need to wait until tomorrow night for a scanner, but I’m currently tracing visible wires using an ohmmeter based on available schematics. I don’t know the connector numbers on the PCM for ASD circuits—that’s exactly what I meant by needing the schematic. The original code reported was P1768. Thank you again—ADET.

Anonymous 2009-09-08 19:23

The van started successfully! I had two connectors accidentally swapped at the back of the IPM (near the fuse box). After correcting this, the vehicle now starts—but it remains in limp mode. I suspect the transmission safety shutdown relay schematic is incorrect. Looking at the diagram, it shows that terminal #30 on the relay should have constant 12V positive from fuse 15 and battery A1, while contact 87 should be grounded (0 volts). In my actual relay, this is reversed—terminal #30 has 0 volts, and contact 87 receives 12V. Additionally, I still observe +12V at pin 4 of the solenoid pressure switch assembly, but the solenoids are not activating or 'chattering'. I will test the solenoids manually tomorrow using a scanner to energize them directly. Thanks for all the help!