The Innova 3120 Obd2/obd1 Code Reader is a popular handheld scanner touted for its broad vehicle compatibility. Many users, however, particularly those working on 94 or 95 F-body cars, have reported problems when using this tool for OBD1 diagnostics. To investigate these claims, we decided to put the Innova 3120 to the test, focusing specifically on its performance with OBD1 systems in these classic vehicles. This review details our findings, highlighting significant issues encountered during OBD1 operation on 94-95 F-cars.
The Innova 3120 arrives neatly packaged in two zippered black plastic cases. One case houses the handheld unit and its OBD2 cable, while the other contains the OBD1 cable and a selection of adapters. Batteries are included, along with a very basic quick-start manual. For more in-depth instructions, the manual directs users to download the full manual from the innova.com website. The scanner itself features a connector at the top for attaching the diagnostic cables. The OBD2 cable is a single, integrated piece, whereas the OBD1 cable is a generic type designed to be used with interchangeable adapters. The display is a blue backlit monochrome LCD, capable of showing approximately ten lines of data at once. The unit is equipped with nine buttons and three LED indicators, and is roughly the size of a standard TV remote control.
Alt text: Innova 3120 OBD2/OBD1 Code Reader kit including handheld unit, OBD2 and OBD1 cables, adapters, and carrying cases.
Initial impressions of the button interface are somewhat negative. The navigation relies solely on UP and DOWN buttons. In menus with multiple options, this necessitates numerous button presses to reach a selection in the middle of a list. Adding to the usability challenges, the DTC display screen only provides a single DOWN navigation button. The standard UP and DOWN buttons on this screen are instead dedicated to scrolling through potentially lengthy DTC description text.
For the purpose of this review, we concentrated our testing on OBD1 functionality with 94 and 95 LT1 F-cars. For comparison and verification, we utilized a Tech 2 clone and the Scan9495 PC application, both known for their reliable OBD1 diagnostics on these vehicles.
Unfortunately, our testing revealed significant problems with the Innova 3120’s OBD1 performance on 94-95 F-cars. Despite these models being explicitly listed as supported vehicles by Innova, the scanner failed to operate correctly. When connected to an LT1 PCM test bench with no fault codes present, the 3120 erroneously reported a long list of DTCs: 45, 44, 43, 42, 41, 55, 54, 53, and 52. While each code was accompanied by a description that matched the number, all of these reported codes were false positives. The scanner should have indicated “No codes” in this scenario. To further investigate, we intentionally introduced a trouble code 22 to the PCM. In response, the 3120 displayed an additional incorrect DTC 34, compounding the initial false readings.
To understand the source of these errors, we employed a data sniffer on the data communication line. This analysis confirmed that the Innova 3120 was indeed sending the correct data request to the PCM, and the PCM was responding with the correct data. The issue clearly lay within the scanner’s interpretation of the data received from the PCM. Extensive testing followed, involving cycling through almost every available setting for years 1993, 1994, and 1995 on the 3120, in an attempt to find a compatible vehicle profile. This process eventually revealed that the scanner was incorrectly using the data-stream definition A219, intended for 4.3L (LB4), 5.7L (L05), and 7.4L (L19) engines in Type C, K, G, and P light/medium duty trucks, instead of the correct 94/95 F-car profile. Every incorrect DTC displayed by the 3120 for various forced trouble codes on our test bench correlated with the DTCs defined for these truck applications. For instance, on the 94 F-car, the bit representing the “Heated Windshield Request ON/OFF” status occupies the same data position as the truck’s DTC 45 set bit.
Alt text: Close-up of the Innova 3120 OBD2/OBD1 Code Reader OBD1 cable and various adapter connectors for different OBD1 vehicle types.
Unfortunately, this cross-referencing approach has limited utility, applicable to only about ten DTCs. This limitation arises because other data unrelated to DTCs is interspersed within the data stream in a way that doesn’t consistently align with the data structure used for other vehicle types. Consequently, creating a comprehensive DTC conversion list to serve as a workaround is impractical. We will continue to explore potential solutions, and we welcome any information from users who may have discovered a vehicle setting on the Innova 3120 that yields accurate readings for 94-95 F-cars.
It is important to note that the specific false DTCs displayed by the 3120 may vary beyond the initial list of nine. This variability is due to the fact that the data bits in the affected data locations can represent dynamic parameters. As an example, the displayed DTCs can change depending on the position of the gearshift selector.
Regarding trouble code erasure for 94-95 F-cars, the Innova 3120 is also ineffective. When attempting to erase codes, the scanner simply displays instructions to follow the vehicle manufacturer’s procedure, such as disconnecting a fuse, rather than performing the erasure function itself.
While our in-depth review focused on OBD1 operation, we anticipate that the Innova 3120’s OBD2 functionality is likely more reliable. However, OBD2 testing was not conducted as part of this specific evaluation.
In conclusion, our tests reveal significant shortcomings in the Innova 3120 OBD2/OBD1 code reader’s OBD1 performance on 94-95 F-body vehicles. The scanner incorrectly interprets OBD1 data for these cars, leading to false DTC readings and rendering it unsuitable for accurate diagnostics on these specific models. Users working on 1994 and 1995 F-cars should be aware of these limitations when considering the Innova 3120 for OBD1 diagnostics.
